Scale Treatment Planning Using Broaching Method in a Vapor-Dominated Geothermal Well X at Kamojang Geothermal Field

Abstract

Scaling in geothermal production wells poses a critical challenge to sustainable energy production, particularly in vapor-dominated systems where scaling mechanisms are less understood. This study investigates scale treatment planning using the broaching method in Well X at Indonesia’s Kamojang geothermal field. Through well integrity testing, geochemical analysis, and XRD characterization, silica (quartz) scale formations were identified in the production casing. Performance monitoring revealed gradual decreases in steam production and wellhead pressure over a three-year period. The selection of the broaching method was validated through analysis of scale characteristics, well geometry, and economic feasibility, offering a significantly more cost-effective solution compared to conventional methods with a substantially shorter payback period. Broaching has effectively operated on multiple geothermal wells, restoring significant production capacity at approximately half the expense of conventional well workover methods. Our results challenge accepted assumptions on scaling in vapor-dominated systems and provide a methodical framework for scale treatment planning. This study demonstrates how strategic scale management can efficiently preserve well productivity while lowering operating costs, thus enabling sustainable geothermal resource development for operators worldwide.

1. Introduction

Unconventional oil and gas resources and green energy such as geothermal energy are important energy sources for maintaining sustainable social development [1]. Geothermal energy generation is widely acknowledged as an essential renewable resource, notably in Indonesia, which has substantial geothermal potential exceeding 23.9 GW [2]. This potential, ranging from low to high enthalpy, extends along volcanic paths from Sumatra through Java, Bali, Nusa Tenggara Timur, Sulawesi, to Maluku. As of 2020, Indonesia’s installed geothermal power plant (GPP) capacity reached 2130.7 MW, utilizing primarily imported technologies [3]. Although this clean energy source provides reliable power throughout the year, scaling in geothermal wells poses significant challenges that can impede efficiency and productivity [4]. Effectively planning scale treatments becomes crucial for maintaining the long-term productivity and economic viability of geothermal operations [2].

Silica scaling is notably common in geothermal systems, arising when dissolved minerals precipitate as a result of fluctuations in pressure, temperature, and chemical conditions during extraction [5,6].

Research has consistently demonstrated that silica precipitation can markedly decrease the efficiency of geothermal-producing wells, resulting in reduced production rates and increasing operational expenses [7]. A study conducted by Setiawan et al. (2019) [8] demonstrated that the regulation of silica precipitation requires optimal pH and temperature conditions. To minimize scaling in cold re-injection systems, temperatures should be maintained at approximately 40 °C, and the pH should be 7 [8]. An understanding of scale formation mechanisms is essential for formulating successful treatment strategies.

Additionally, Boersma emphasizes scale prevention with innovative materials such as glass-fiber-reinforced composites with epoxy or polyethylene inner surfaces, which provide improved scale resistance relative to conventional steel pipes [9]. Scale inhibitors, which act as an alternative approach to prevent cation aggregation, must be applied in precise dosing to avert by-product precipitation. Although initial expenses are increased, these sophisticated materials offer a more sustainable approach to scale management. Yet, creating effective inhibitors for silica and heavy-metal sulfides continues to pose difficulties [10].

Chemical and material-based strategies provide preventive measures for scaling problems, whilst mechanical interventions such as broaching have proven to be an effective corrective remedy. For example, broaching has effectively operated on 14 geothermal wells, restoring over 22 MW of production at around 50% of the expense of a conventional well workover. This illustrates broaching’s capability to sustain operational efficiency while markedly decreasing maintenance expenses, corroborating its designation as a cost-effective option [11].

However, the literature review reveals significant knowledge gaps in vapor-dominated geothermal systems, particularly in scale formation and treatment mechanisms [12]. Despite substantial studies on liquid-dominated systems, there is a lack of comprehensive planning frameworks and economic evaluations for vapor-dominated fields, underscoring the necessity for systematic research that addresses both technical and economic dimensions of scale treatment.

This study identifies significant knowledge gaps and employs a thorough methodology for vapor-dominated systems, incorporating well integrity testing, XRD analysis, and economic assessment. In the case study of Well X at Kamojang, characterized by scale formation at a depth of 900.74 m, with a thickness of 252.7 mm (9.95 inches) and an inclination of 30°, broaching techniques were optimized alongside a comprehensive economic analysis of treatment methods for vapor-dominated systems.

This study advances academic knowledge and practical applications through five key objectives: developing a comprehensive scale removal methodology using broaching, assessing economic viability, optimizing techniques for specific wells conditions, establishing treatment guidelines, and creating monitoring frameworks. These contributions aim to enhance geothermal well maintenance efficiency, offering cost-effective solutions while advancing sustainable geothermal resource management.

2. Geothermal System and Tectonic Setting of Kamojang Field

The Kamojang geothermal field, operating since 1983, is located approximately 40 km south of Bandung in West Java, Indonesia. The temperatures range from 15 to 20 °C with the annual rainfall reaching 2885 mm [13]. As Indonesia’s first geothermal exploitation site, Kamojang began with a 0.25 MW Monoblock turbine generator at well KMJ-6 in 1978, followed by the first commercial unit of 30 MWe in 1982. The field demonstrates remarkable potential with a current installed capacity of 235 MW across five generating units utilizing a single-flash system [14]. The power generation is distributed among multiple operators: PT. Indonesia Power manages Units 1, 2, and 3 (with capacities of 30 MW and 55 MW, respectively), while PT. Pertamina Geothermal Energy operates Units 4 and 5 (60 MW and 35 MW). Additionally, the Agency for the Assessment and Application of Technology Indonesia (BPPT) operates a pilot-scale facility [15]. The reservoir characteristics are distinctive, with temperatures, ranging from 230 to 245 °C, and pressures of 30–37 bar, causing geothermal fluid to fluctuate between compressed liquid and superheated states along the saturation line [16]. In this single-flash system, wellhead fluid exists as a saturated liquid before entering a separator where pressure reduction leads to phase separation, maintaining constant enthalpy while increasing entropy [15]. Despite being traditionally considered less prone to scaling compared to liquid-dominated systems, recent studies have revealed significant scaling problems that potentially affect long-term production sustainability [17].

Located within the western Indonesian archipelago, the Kamojang geothermal system emerges from the dynamic convergence between the Indian–Australian Ocean Plate and the Eurasian Continental Plate [18]. The tectonic evolution of the region since the Eocene has resulted in unique structural patterns throughout Indonesia’s principal islands. Sumatra exhibits oblique subduction accompanied by a corresponding fault system [19]. Java, on the other hand, has a perpendicular subduction pattern that has created unique east–west-trending physiographic zones [20,21,22].

The tectonic architecture of Java demonstrates distinctive structural patterns [23] characterized by three primary lineament systems: the Meratus Pattern (northeast–southwest), Sunda Pattern (north–south), and Java Pattern (east–west). These structural elements have shaped the development of an extensive magmatic belt from the Late Eocene to Quaternary periods. This belt features diverse magmatic compositions ranging from tholeiitic series to calc-alkaline and shoshonitic varieties [24].

One of the forty identified geothermal prospects in the region is the Kamojang geothermal field, which is situated within the quaternary volcanic belt of West Java [25]. Geothermal activity in the region is primarily concentrated in two main zones: the salak corridor and the Galunggung–Tangkuban Prahu belt (Figure 1). Within the Pleistocene age of the Pangkalan caldera structure, Kamojang, along with the Darajat and Wayang Windu systems, comprise the Kendang volcanic complex [26].

An east–west trending volcanic chain defines the local geology, encompassing several volcanic edifices: Mt. Rakutak, Ciharus Lake, Pangkalan Lake, Mt. Gandapura, Mt. Guntur, and Mt. Masigit. Volcanic activity in the region spans from 1.2 to 0.452 Ma, as determined by radiometric dating [27]. The volcanic sequences predominantly consist of basaltic to andesitic compositions [28], with the main thermal up-flow zone centered in the Kamojang area [29].

Figure 1. Distribution of the Quaternary volcano segment’s boundary zone in West, Central, and East Java Island (Latitude: −7.152541°; Longitude: 107.791216°) (Modified from [28]).

Figure 1. Distribution of the Quaternary volcano segment’s boundary zone in West, Central, and East Java Island (Latitude: −7.152541°; Longitude: 107.791216°) (Modified from [28]).

The hydrothermal system of the field exhibits complicating alteration patterns indicative of both acidic and neutral pH environments [30,31]. A specific vertical zonation pattern encompasses argillic and propylitic domains [32]. The distribution of clay minerals in the argillic zone is governed by temperature. Kaolin is produced below 120 °C, smectite forms below 150 °C, and smectite–illite assemblages develop beyond 200 °C. Various forms of silica, particularly quartz, are present in various regions. This indicates the presence of active silica transport pathways, which may lead to scaling problems throughout production.

3. Methods

This chapter outlines the scientific framework utilized to examine scaling issues in geothermal wells, specifically concentrating on Well X in PT. Pertamina Geothermal Energy Area Kamojang. The research technique includes methodical approaches to data collecting, analysis, and assessment, offering a thorough understanding of scaling phenomena and associated treatment choices in geothermal well operations.

3.1. Research Location

This research was conducted at PT. Pertamina Geothermal Energy Area Kamojang, situated in Laksana, Ibun, Bandung, West Java (Figure 2). This site was strategically selected because of its substantial scale formation challenges and its exemplification of vapor-dominated geothermal systems. This study included field data gathering under diverse operating settings and enabled a comprehensive understanding of scaling phenomena in geothermal well operations.

Among the production wells studied in this field, Well X, as shown in Figure 3, is classified as a big hole type. The well is situated at an elevation of 1483 m above sea level and reaches a measured depth (MD) of 2501 m, with a true vertical depth (TVD) of 2225.26 m. The reservoir conditions indicate a pressure of 26.5 bar and a temperature of 230 °C. These specifications characterize Well X as a significant production asset in the geothermal field, providing essential baseline parameters for analyzing its performance and scaling issues.

3.2. Research Methods

This study implemented an integrated methodological approach integrating quantitative data evaluation, laboratory analysis, and field observations. Direct field measurements, well integrity testing, scale sample collecting, and geochemical fluid sampling were the primary data-collecting procedures [33]. Secondary data from past treatment records, historical well performance records, and relevant technical specifications were added to these main data sources. This holistic methodology guaranteed data validity through several verification techniques and allowed a thorough study of scaling issues.

Figure 4 illustrates the systematic progression of the research, which commenced with an initial assessment and literature review to establish foundational knowledge on geothermal scaling mechanisms. This was followed by field data collection, including well integrity testing through Go-Devil operations and sample catcher deployments to retrieve scale samples at precise depths (900.74 m). Subsequent phases focused on laboratory analysis, where scale samples underwent geochemical characterization, XRD analysis, and scale type determination to identify silica (quartz) as the primary deposit. These analytical outcomes informed the treatment method selection, where the broaching method was validated as optimal based on technical feasibility, economic viability (USD 42,690 vs. conventional methods), and compatibility with the well’s 30° inclination. The final stages involved broaching method design, tailored to the casing geometry and scale thickness 252.7 mm (9.95 inches), and implementation planning to ensure operational safety and efficiency.

3.2.1. Geochemical Sampling

Steam from production wells serves as the primary resource for power generation at this geothermal facility [34]. The wells produce high-quality single-phase steam with 98.9% dryness, essential for efficient power generation [35]. PGE Kamojang’s laboratory conducts regular steam sampling and analysis using four main testing methods to maintain optimal performance. The comprehensive analysis includes cation measurement using ICP and AAS instruments, anion testing through Ion Chromatography (with titration as an alternative for high chloride samples), gas content analysis via Gas Chromatography or acid titration, and CO₂ base analysis using spectrophotometry with a focus on ammonia content [36]. This systematic testing protocol ensures the steam meets quality standards necessary for efficient power generation and equipment protection.

At the Kamojang geothermal field, a comprehensive sampling protocol encompasses steam and gas collection from production wells. Steam sampling is conducted during well operation, with the single-phase dry Total Flow Steam (TFS) collected directly from the steam pipeline and condensed into polyethylene bottles [37,38]. This approach is tailored to the unique characteristic of Kamojang, which produces exclusively single-phase dry steam.

Gas sampling occurs concurrently with well operation, employing a direct collection method without separation. The procedure utilizes a T-rod assembly directly linked to the side valve or connected via specific sampling points along the steam pipeline. The gas is directed into collection vessels containing a 35% sodium hydroxide (NaOH) solution, which ensures the effective capture and preservation of gas components for subsequent analysis as shown in Figure 5 [39].

All sampling procedures follow ASTM D1066-97 standard methodology, ensuring consistency and reliability in sample collection and analysis. This standardized approach enables accurate steam quality assessment and maintains proper quality control protocols [38].

These regular quality checks help maintain optimal operating conditions, prevent equipment damage, and ensure consistent power generation performance. The testing program provides essential data for daily operations and long-term maintenance planning, ultimately supporting sustainable geothermal power production.

3.2.2. Scale Analysis Methods

Scale analysis encompassed multiple analytical approaches to characterize the scaling phenomena comprehensively. Mineral composition was identified through XRD analysis, while formation mechanisms were assessed through the correlation of operational parameters and geochemical data [40]. The severity of scaling was evaluated through well performance indicators and physical measurements, enabling quantitative assessment of scale impact on well productivity [41]. Production data analysis included a detailed examination of well performance trends, pressure and flow rate correlations, and decline curve analysis, providing crucial insights into the scale formation patterns and their operational impacts [42]. In addition to this method, water samples were analyzed for cations (K, Na, Mg, Ca, Li, B) using Inductively Coupled Plasma–Optical Emission Spectrometry (ICP-OES) and for anions (SO₄, F, Cl, NO₃) using ion chromatography. Gas samples were analyzed using gas chromatography for unreactive gasses (H₂, Ar, N₂, CH₄) and titration methods for reactive gasses (CO₂, NH₃, H₂S). Besides that, the analytical methodology involved non-chemical sample preparation through agate mortar grinding and oven drying, followed by bulk XRD analysis of materials collected via the 5.5″ sample catcher in well “X” locations in the Kamojang geothermal field. The samples were analyzed using a Rigaku MiniFlex II (Cu Kα radiation, λ = 1.5418 Å, operating at 30 kV and 15 mA). Diffraction patterns were collected over a 2θ range of 5–80° with a step size of 0.02° and a scan speed of 0.5°/min. The data were analyzed using Jade^® 9.0, and mineral identification was performed using the COD-Inorg 2023.12.05 (Crystallography Open Database). Quantitative phase analysis (QPA) was conducted via the Rietveld refinement method to determine the weight percentages of crystalline phases.

3.2.3. PHREEQC Analysis

The chemical water samples were used for chemical thermodynamic modeling with PHREEQC 3.7.3.15968 [43]. The PHREEQC software simulation provided saturation index (SI) values for various minerals that might form in the brine samples. These SI values show how saturated different minerals are in the brine, which helps us understand the potential for scaling. The SI values come from the geochemical field data we collected earlier. This analysis gives us a more detailed look at which minerals in the brine might cause scaling problems.

3.3. Treatment Method Selection

Treatment method selection followed a systematic evaluation process incorporating multiple criteria. Technical feasibility was assessed based on well conditions and scale characteristics, while economic considerations encompassed immediate implementation costs and long-term operational implications.

4. Results and Discussion

4.1. Scale Formation Indicators in Well X

4.1.1. Analysis of Wellhead Pressure (WHP) Decline Indicators

Initial evidence of scaling in Well X was identified through the systematic monitoring of wellhead pressure decline over specific periods. This pressure reduction can be attributed to wellbore diameter constriction and increased frictional resistance caused by scale deposition [44]. This analysis outlines the WHP patterns recorded in Well X during three successive monitoring periods, illustrating the temporal progression of pressure decrease characteristics. The pressure monitoring data provides crucial diagnostic information for evaluating the progression of scale formation within the wellbore system [45].

The evolution of wellhead pressure data, as shown in Figure 6, reveals a notable declining trend beginning in 2021. This pressure reduction may be attributed to scaling formation or other well integrity issues. The observed WHP decline could stem from multiple factors such as reservoir depletion, wellbore integrity issue, scale formation, etc. However, comprehensive well integrity testing was conducted, to definitively attribute this pressure reduction to scale formation [46].

4.1.2. Analysis of Production Decline Characteristics

Figure 7 illustrates the correlation study between steam flow rate and wellhead pressure trends. The plotted data reveals that while steam production rates showed a moderate decline of approximately 8.9% over three years, a notable reduction in wellhead pressure was observed in 2022. The small decrease in production at Well X creates an uncertain diagnostic situation. The existing production data alone provides no conclusive evidence to ascribe the performance decline, especially to scaling phenomena. Consequently, thorough well integrity testing was considered essential to validate the root cause of the observed changes and conclusively determine the presence and effects of scale formation [46].

4.2. Scale Formation Assessment Through Well Integrity Testing: Go-Devil and Sample Catcher Analysis

Well integrity testing was conducted to verify scaling issues in Well X, determine the precise depth of scale deposits, and obtain physical samples for laboratory analysis of scale composition [47]. The investigation was conducted on Well X, which features a well architecture comprising multiple casing strings: a 762 mm (30 inches) conductor casing extending from the surface to 30 MD, 508 mm (20 inches) surface casing reaching 390 MD, and a 339.7 mm (13-3/8 inches) production casing that extends to 901 MD. The lower section consists of a 273.05 mm (10 3/4 inches) liner extending from 901 to 1800 MD, and a 219.075 mm (8 5/8-inches) liner from 1800 to 2500 MD, culminating in a total measured depth of 2500 MD (true vertical depth of 2225.26 MD). The kick-off point of the well is located at 250 MD. The well integrity assessment program employed a 203.2 mm (8 inches) go-devil tool, chosen following the existing casing dimensions. The investigation focused on the complete wellbore length of 2500 MD, with measurements taken over a duration of approximately two hours during a shut-in period. This evaluation offered diagnostic data on scale accumulation and physical samples for further laboratory analysis [48].

4.2.1. Analysis of Go-Devil Measurement Results

Go-devil operations were implemented as a diagnostic tool to identify wellbore diameter anomalies and constrictions by analyzing tool movement and sticking points at various depths [49] as shown in Figure 8. The initial setting depth of the tool serves as a primary indicator of wellbore constriction zones. The diagnostic assembly consisted of multiple components carefully selected for optimal performance and reliable data collection. The tool string configuration included a 45 cm go-devil tool (5.40 kg), a 200 cm jar assembly (7.25 kg), a 10 cm socket (0.40 kg), a 45 cm extension sinker (1.95 kg), and a 20 cm bull nose (0.90 kg) (Figure 8). The operation utilized a slickline with specifications of 23.37 mm (0.92 inches) and 2.74 mm (0.108 inches) diameters, rated for maximum tensions of 640 kg and 930 kg, respectively, ensuring operational safety and measurement accuracy.

The well integrity assessment utilized a carefully designed tool assembly measuring 3.2 m in total length. This assembly integrated five essential components: a 45 cm go-devil tool, 200 cm jars, a 10 cm socket, a 45 cm extension, and a 20 cm bull nose. The complete assembly weighed 15.00 kg, with weight distribution across components as follows: go-devil tool (5.40 kg), jars (7.25 kg), socket (0.40 kg), extension (1.95 kg), and bull nose (0.90 kg).

The initial diagnostic operation took place from 02:00 to 03:30 GMT, utilizing a 203.2 mm (8 inches) go-devil tool. In the initial Run-In-Hole (RIH) phase, the tool descended smoothly to a maximum depth of 900.04 m, encountering no obstacles. However, the Pull-Out-Of-Hole (POOH) phase demonstrated notable wellbore constrictions. The tool was immobilized at a depth of 900.04 m, necessitating several jar-up operations for its retrieval. A second obstruction was encountered at 369.07 m, which was similarly addressed through repeated jarring operations. Upon overcoming these obstacles, the tool was successfully retrieved to the surface without additional incidents.

A subsequent operation was performed from 16:10 to 17:10 WIB using a 63.5 mm (2.5 inches) sinker. This procedure achieved a slightly deeper penetration to 901.00 m and, notably, encountered no obstructions during either the descent or retrieval phases. The scale in the well depth illustrated in Figure 9 provides crucial data points for mapping the scale formation zones and characterizing the extent of wellbore constrictions, essential information for planning future well intervention strategies [50].

4.2.2. Analysis of Sample Catcher Measurement Results

After identifying scale deposit anomalies at 900.74 m, a systematic sampling operation was conducted utilizing two distinct sample catcher configurations. The initial sample collection employed a 139.7 mm (5.5 inches) sample catcher, targeting the scale formation at 900.04 m. This was followed by a second sampling phase using an 88.9 mm (3.5 inches) sample catcher, specifically designed to collect samples at 900.74 m. The sampling procedure was conducted over approximately four hours to ensure comprehensive sample collection and tool manipulation at both target depths.

A comprehensive scale sampling operation was conducted utilizing two distinct tool configurations to ensure thorough sample collection at the identified scale formation depth. As shown in

Table 1. Data tool scale catcher.

Data Tools Sample Catcher SC
Tools	Length	Weight
Scale Catcher 5.5″	60 cm	3.50 kg
Scale Catcher 3.5″	60 cm	2.00 kg
Jars	200 cm	7.25 kg
Socket	10 cm	0.40 kg
Extension sinkers	45 cm	1.95 kg
Bull Nose	20 cm	0.90 kg
Slickline 0.92″. Max Tension 640 kg 0.108″. Max 930 kg

and Figure 10, the initial deployment employed a 139.7 mm (5.5 inches) scale catcher assembly, engineered with a total length of 3.35 m and comprising five integrated components: a 60 cm scale catcher (3.50 kg), 200 cm jars (7.25 kg), a 10 cm socket (0.40 kg), a 45 cm extension (1.95 kg), and a 20 cm bull nose (0.90 kg), yielding a total assembly weight of 13.1 kg.

The first sampling operation, conducted from 04:30 to 05:45 GMT, successfully reached the target depth of 900.74 m, retrieving both solid scale deposits and fluid samples. During the retrieval phase, the tool encountered significant resistance at two distinct points: 900.04 m and 369.07 m, necessitating repeated jarring operations to overcome these obstacles. A subsequent operation utilizing an 88.9 mm (3.5 inches) scale catcher (Figure 11) assembly of identical length but reduced weight (12.5 kg) was performed from 13:50 to 15:10 WIB, targeting the same depth. While this second run encountered similar obstruction points during retrieval, it did not yield additional samples.

The physical analysis of the retrieved samples indicated the presence of distinctive white layered scale deposits, approximately 1 cm in size, collected from an environment with a wellhead pressure of 24.9 bar and a temperature of 205.17 °C. The fluid observed in the 139.7 mm (5.5 inches) tool samples was linked to wellbore condensation processes, as recorded by PGE Kamojang, offering a further understanding of the downhole environmental conditions. The findings, along with the consistent depth of mechanical obstacles encountered during both runs, support the existence and characteristics of scale formation at the specified depths.

4.2.3. Well Schematic Analysis of Scale Deposition Points Based on Well Integrity (Go-Devil) Measurements

The comprehensive well integrity assessment conducted on Well X revealed detailed characteristics of scale deposition through systematic diagnostic operations. The initial deployment of a 203.2 mm (8 inches) go-devil tool identified a significant restriction at 900.74 m, which was subsequently confirmed through successful scale sample retrieval at the identical depth, definitively establishing the upper boundary of scale formation. A secondary diagnostic run utilizing a 63.5 mm (2.5 inches) go-devil tool penetrated marginally deeper to 901.00 m, effectively delineating the lower boundary of the scale accumulation zone and providing crucial vertical profiling of the deposition pattern.

An analysis of the production casing configuration ((339.7 mm (13-3/8 inches) L-80, 68 ppf, BTC R3) and scale formation characteristics indicated significant internal diameter reduction. The casing specifications disclose an outer diameter of 339.7 mm (13.375 inches) and an inner diameter of 315.3 mm (12.415 inches). The remaining effective internal diameter was determined to be 251.8 mm (9.915 inches) through a precise calculation methodology that included go-devil measurement data and casing specifications, indicating a significant scale thickness of 251.8 mm (9.915 inches). The scale deposits were identified primarily as silica-based formations, aligning with the geothermal well environment and its operational history.

This detailed structural mapping and dimensional analysis, as illustrated in the well schematic (Figure 9) and scale thickness simulation (Figure 11), provides essential technical parameters for future well intervention strategies [51]. The precise delineation of scale accumulation zones, coupled with quantitative thickness measurements, establishes a robust foundation for designing targeted scale removal operations and implementing effective well-stimulation programs [52]. These findings represent critical baseline data for maintaining the well’s integrity and optimizing future production performance through informed intervention planning.

4.3. Scale Formation Assessment Through Geochemistry and XRD Analysis

Understanding scale formation in geothermal wells requires a systematic analysis of fluid chemistry and mineral composition. This assessment combines geochemical sampling techniques with advanced X-ray diffraction (XRD) analysis to provide a comprehensive characterization of scale deposits and their formation mechanisms [53]. The integration of these methodologies enables the accurate identification of scale composition and its relationship to well-fluid chemistry, essential for developing effective scale management strategies.

4.3.1. Geochemistry Result and Scaling Prediction

The geochemical evolution observed in the Kamojang geothermal field from July 2019 to November 2021 reveals significant implications for mineral scaling phenomena as shown in

Table 2. Fluid geochemistry Well X.

Well Name	KMJ-X	KMJ-X	KMJ-X	KMJ-X	KMJ-X	KMJ-X	KMJ-X	KMJ-X
Type of Well	PROD	PROD	PROD	PROD	PROD	PROD	PROD	PROD
Sampling Date	21 July 2019	27 August 2019	28 November 2019	27 March 2020	8 December 2020	18 March 2021	10 August 2021	9 November 2021
Conductivity µS/cm	16.60	23.55	24.60	27.00		20.00	21.00	25.00
pH at TEMP 25°	4.75	4.60	4.51	4.31	3.91	4.41	4.32	4.04
TDS (ppm)	1.28	1.13	0.80	0.82	2.15	1.28	0.96	0.69
Sodium (Na) (ppm)	0.20	0.10	0.04	0.03	0.03	0.08	0.03	0.03
Potassium (K) (ppm)	0.20	0.10	-	-	-	-	-	-
Calcium (Ca) (ppm)	0.05	0.05	-	-	-	-	-	-
Magnesium (Mg) (ppm)	0.05	0.05	0.01	0.01	0.02	0.02	0.02	0.02
Lithium (Li) (ppm)	0.05	0.05	-	-	-	-	-	-
Ammonium (NH4) (ppm)	1.73	2.16	-	-	-	-	-	-
Iron (Fe) (ppm)	0.01	0.05	0.07	0.01	0.43	0.03	0.02	0.03
Fluor (F) (ppm)	0.21	0.20	0.26	0.20	0.21	0.29	0.30	0.21
Bicarbonate (HCO3) (ppm)	7.44	9.24	-	-	-	-	-	-
Chloride (Cl) (ppm)	0.01	0.14	0.09	0.11	0.04	0.79	0.10	0.05
Sulfate (SO4) (ppm)	0.67	0.84	0.35	0.52	1.51	0.32	0.45	0.35
Hydrogen Sulfide (H2S) (ppm)	16.63	26.53	-	-	-	-	-	-
Boron (B) (ppm)	4.76	4.82	4.19	3.97	5.31	4.24	5.21	4.60
Silica (SiO2) (ppm)	0.05	0.06	0.24	0.14	0.18	0.06	0.41	0.26

. The decline in pH from 4.75 to 4.04, coupled with fluctuating total dissolved solids (0.69–2.15 mg/L), indicates dynamic reservoir conditions. As shown by Scott et al. (2024), silica polymerization kinetics are influenced by both pH and the degree of supersaturation of the geothermal fluid [54].

Notably, the non-condensable gas composition (

Table 3. NCG composition in Well X.

Date	CO2	H2S	NH3	Ar	N2	CH4	H2	Air Cont	Total NCG
	% Moles								(% wt)
28 November 2019	93.96	3.25	0.03	0.01	0.93	0.13	1.69	-	0.56
27 February 2020	95.02	3.06	0.06	0.00	0.54	0.11	1.21	-	0.61
8 December 2020	95.84	2.54	0.05	0.00	0.55	0.08	0.93	0.01	0.71
19 March 2021	95.06	3.00	0.05	0.01	0.59	0.09	1.20	0.00	0.65
10 August 2021	95.57	2.24	0.05	0.00	0.71	0.12	1.31	0.01	0.72

) exhibits predominant CO₂ concentrations (93.96–95.84%) and a substantial hydrogen sulfide content (2.24–3.25%), with total gas concentrations exhibiting an increasing trend from 0.56% to 0.72%. These geochemical transitions potentially exacerbate scaling mechanisms through dual pathways: CO₂ degassing-induced pH perturbations generate localized supersaturation zones conducive to mineral precipitation, while hydrogen sulfide presence facilitates nucleation sites for scale formation [55].

Based on

Table 4. PHREEQC analysis.

Phase	SI	log IAP	log K(443 K, 8 atm)
Anhydrite	−4.85	−11.15	−6.30	CaSO4
Aragonite	−7.30	−17.80	−10.50	CaCO3
Calcite	−6.42	−17.80	−11.38	CaCO3
CH4(g)	−62.12	−64.96	−2.84	CH4
Chalcedony	−3.66	−6.08	−2.42	SiO2
Chrysotile	−20.73	−0.80	19.93	Mg3Si2O5(OH)4
CO2(g)	−1.84	−3.92	−2.08	CO2
Dolomite	−12.37	−35.39	−23.02	CaMg(CO3)2
Fe(OH)3(a)	−5.52	−0.63	4.89	Fe(OH)3
FeS(ppt)	−60.27	−64.19	−3.91	FeS
Fluorite	−6.03	−16.26	−10.23	CaF2
Goethite	3.84	−0.63	−4.47	FeOOH
Gypsum	−5.80	−11.15	−5.35	CaSO4:2H2O
H2(g)	−18.16	−21.07	−2.92	H2
H2O(g)	0.88	0.00	−0.88	H2O
H2S(g)	−57.15	−65.51	−8.36	H2S
Halite	−13.27	−11.62	1.65	NaCl
Hematite	10.14	−1.26	−11.41	Fe2O3
Jarosite-K	−15.17	−31.89	−16.72	KFe3(SO4)2(OH)6
Mackinawite	−59.54	−64.19	−4.65	FeS
Melanterite	−11.91	−13.41	−1.50	FeSO4:7H2O
O2(g)	−15.77	−18.75	−2.98	O2
Pyrite	−96.43	−112.19	−15.77	FeS2
Quartz	−3.54	−6.08	−2.54	SiO2
Sepiolite	−23.87	−10.67	13.20	Mg2Si3O7,5OH:3H2O
Sepiolite(d)	−29.32	−10.67	18.65	Mg2Si3O7,5OH:3H2O
Siderite	−8.58	−20.06	−11.48	FeCO3
SiO2(a)	−4.17	−6.08	−1.91	SiO2
Smithsonite	−7.92	−18.96	−11.04	ZnCO3
Sphalerite	−53.45	−63.09	−9.64	ZnS
Sulfur	−43.81	−41.21	2.60	S
Sylvite	−13.24	−11.85	1.39	KCI
Talc	−23.25	−12.96	10.29	Mg3Si4O10(OH)2
Willemite	−8.57	−1.24	7.33	Zn2SiO4
Zn(OH)2(e)	−9.08	2.42	11.50	Zn(OH)2

, the analysis results indicate that the brine samples in the surface have the potential to form several minerals, as calculated by PHREEQC software using its available mineral database. Although many types of minerals were analyzed, only a few have saturation index (SI) values above zero, indicating potential for scaling formation. The minerals with SI values above zero in the brine samples are Goethite and Hematite.

a.

Goethite (FeO(OH))

Goethite is an iron mineral that can form under certain conditions in water or brine containing iron. Goethite tends to precipitate at specific pH levels, especially in environments with relatively high oxygen contents.

b.

Hematite (Fe₂O₃):

Hematite is an iron oxide mineral that can also form in brine with high iron concentrations under specific conditions. Hematite is commonly found in oxidizing environments and has the potential to form scales on pipe surfaces or equipment.

Based on the analysis showing that both minerals have SI > 1, this indicates that these minerals could precipitate from the brine solution if the environmental conditions support it (e.g., temperature, pressure, and brine chemical composition). The formation of goethite and hematite in the system could lead to scaling, which in turn could affect fluid flow, process efficiency, and the lifespan of the equipment used.

4.3.2. XRD Analysis and Result

X-ray diffraction (XRD) analysis was employed to characterize scale deposits in Well X, utilizing a systematic analytical protocol comprising mechanical pulverization and digital diffractogram interpretation [55,56]. The investigated scale specimens retrieved from the production casing at 900.74 m depth under specific thermodynamic conditions (24.9 barg, 205.17 °C), exhibited distinctive morphological features: predominantly white coloration with brownish-black sections and laminar structure approximately 1 cm in dimension.

XRD analysis of scale samples from Well X (sample code LB21017-1) definitively identified two distinct mineral phases: quartz (SiO₂) and magnetite (Fe₃O₄) as shown in Figure 12. The diffraction patterns, as illustrated in the analytical curve, confirmed the presence of these crystalline phases, with characteristic peaks corresponding to both minerals. Based on the mineralogical distribution analysis, the predominant scale type in Well X is classified as silica scale, primarily due to the presence of quartz, a principal silica mineral. The co-occurrence of magnetite (Fe₃O₄) suggests a complex scaling mechanism involving both siliceous and ferrous components. This silica scaling phenomenon typically occurs due to pressure and temperature changes during fluid ascent in the wellbore, where the solubility of silica decreases significantly as the geothermal fluid cools and depressurizes. The process is further enhanced when fluid temperature drops below 340 °F (171.1 °C), causing dissolved silica to precipitate as amorphous silica, which eventually crystallizes into quartz [53,57]. The presence of magnetite suggests concurrent iron oxide precipitation, possibly due to oxidation reactions in the production system. This mineralogical assemblage indicates that the scaling mechanism is primarily driven by thermodynamic changes in the wellbore [58,59], requiring careful consideration of pressure and temperature management for effective scale prevention strategies.

The result is that the geothermal operation at Well X in the Kamojang field is characterized by a dynamic interplay of geochemical, thermodynamic, and environmental factors, where silica (quartz) scaling predominates at a depth of 900.74 m within the 339.7 mm (13-3/8 inches) production casing, driven by the rapid reduction in pressure from 26.5 bar in the reservoir to 16.49 bar at the wellhead, and cooling from reservoir temperatures of 230–245 °C to a surface temperature of 199 °C as the fluid ascends. These conditions significantly reduce silica solubility, triggering its precipitation as quartz deposits in the wellbore. Meanwhile, discrepancies between the downhole XRD results, which identify silica (quartz) and magnetite (Fe₃O₄) as the dominant scale components, and the surface-based PHREEQC predictions, which indicate potential precipitation of goethite (FeO(OH)) and hematite (Fe₂O₃), underscore the influence of differing environmental conditions: reducing conditions at depth favor the formation of magnetite, while oxidizing conditions at the surface, combined with oxygen exposure during sampling and the chemical evolution of the brine, promote the precipitation of ferric iron minerals such as goethite and hematite.

4.4. Determination of Scale Cleaning Stimulation Methods

The selection of appropriate well-scale cleaning methods in geothermal operations is a complex process that necessitates careful consideration of several critical factors. Various cleaning techniques are employed, including reaming, high-pressure water injection (roto jet), acidizing, and broaching, each with specific applications depending on the operational context [60]. Extensive field experience, particularly in the Kamojang geothermal field, has identified three primary factors that significantly influence the selection of these methods.

The first factor is the type and hardness of the scale present. Different scales, such as ammonium bicarbonate, silica, and calcite, exhibit varying hardness levels and thicknesses, which dictate the choice of cleaning method [52]. For instance, chemical cleaning is effective for removing ammonium bicarbonate scales, while silica and calcite scales can be addressed through methods such as broaching, roto jets, mechanical reaming, coiled tubing, or acidizing. In cases of particularly hard scales, mechanical methods such as reaming are preferred [11,61,62]. This evidence observed in the use of abrasive water jet (AWJ) technology has been shown to significantly reduce the time required for reaming compared to conventional methods, as demonstrated in the Gonghe geothermal well [61]. For example, in Well X, which has a silica scale (Quartz SiO₂) with a column height below 1 m and a thickness of approximately 228.6 mm (9 inches), the broaching method has been deemed suitable based on these physical characteristics.

The second critical factor is the well deviation and the location of the scale deposits. Directional wells with high deviation angles present unique challenges for stimulation methods that involve string assemblies [11]. Such assemblies may encounter maneuverability issues at the kick-off point (KOP), increasing the risk of collisions and casing leakage. Field experience has shown that broaching operations should be avoided in wells with a deviation exceeding 50 degrees, as the operational risks become significantly increased [63].

The third and arguably most crucial factor is the operational costs associated with the cleaning methods as seen in

Table 5. Scale stimulation cost comparison [11,65].

Stimulation Method	Cost
Drilling equipment	USD 1,195,339
Coiled Tubing Hole cleaning	USD 866,181
Bull heading	USD 628,147
Broaching	USD 42,690

and

Table 6. Cost prediction breakdown for the broaching method.

Cost Component	Cost (USD)	Details
Broaching Tools	5000	Single-use tools (3.5″–5.5″)
Slickline unit Mobilization	15,000	1 day of rig time at USD 15,000/day.
Labor	8000	2 technicians × 2 days × USD 2000/day.
Fluid Circulation	2000	Brine or water used for debris flushing during operation.
Well Downtime	12,690	1 day of lost production: 689 tons/day × USD 18.40/ton (steam price).
Total Cost	42,690	Sum of all components.

. The economic viability of the broaching method is demonstrated through comparative revenue analysis. With an initial investment of USD 42,690, the intervention restored Well X’s steam production from 28.71 to 31.50 tons/hour. Assuming a plant availability factor of 35% (accounting for operational downtime and maintenance), the daily revenue increased by USD 431.22 (steam price: USD 18.40/ton). This results in a monthly revenue gain of USD 12,936.63, yielding a payback period of 3.3 months. In contrast, conventional methods (USD 628,147–USD 1,195,339) would require 4–10 years for cost recovery under similar conditions. Broaching’s rapid return on investment, coupled with reduced downtime, establishes it as the optimal scale treatment solution for Well X. The economic efficiency of these methods plays a pivotal role in decision-making processes. It is essential to balance the cost of implementation against the potential production improvements that result from the cleaning operations. Expensive methods that yield low success rates or minimal production enhancements can severely strain company resources [64]. Therefore, a thorough evaluation of the cost structures of various cleaning methods and their expected outcomes is necessary to ensure economic viability [53].

4.5. Planning for Broaching Scale in Well X

Scale broaching planning in Well X is conducted to evaluate the method’s feasibility and establish operational guidelines for future company implementations. The effectiveness of this method relies on three critical operational parameters that require continuous monitoring. The first parameter is wireline speed (ft/min), which must be precisely controlled during descent and ascent operations to prevent line failure due to excessive or insufficient velocity. The second parameter is depth (ft), which requires constant surveillance to track the broaching tool’s position and identify scale locations within the wellbore. The third and most crucial parameter is tension (lbs), which measures the stress experienced by the wireline [11]. Tension typically increases proportionally with depth but exhibits a characteristic of decreases when the tool encounters scale deposits. During jarring operations, tension displays a distinctive oscillating pattern. The definitive indicator of scale detection is a decrease in tension, signifying the broaching tool’s contact with scale deposits, at which point jarring operations are immediately initiated to remove the obstruction.

4.5.1. Requirements for Broaching Operations to Be Used in a Well

The feasibility of broaching operations is determined by three critical factors: scale composition, scale thickness within the casing, and well deviation. In terms of scale composition, broaching can effectively remove calcite and silica deposits, although operational difficulty increases with scale hardness and thickness [11]. In Well X’s case, the scale characteristics fall within acceptable parameters for broaching implementation. Regarding scale thickness within the casing, Well X exhibits a constriction that reduces the internal diameter to approximately Broaching 63.5 mm (2.5 inches), which remains within operational limits for various broaching tool sizes, making the mechanical scale removal viable. Well X’s deviation represents another crucial consideration, as highly deviated or horizontal wells significantly complicate broaching operations and reduce their effectiveness. Well X’s deviation angle and kick-off point (KOP) are within acceptable limits for successful broaching operations. The aforementioned factors suggest that broaching is an appropriate method for scale removal in Well X.

4.5.2. Determination of Broaching Based on Well X’s Deviation Angle

The deviation analysis of Well X demonstrates optimal geometric conditions for broaching operations. As shown in Figure 13a,b, the well’s architecture begins its deviation at a Kick-Off Point (KOP) of 144 MD, extending to a total depth of 2501 MD. The deviated section length, calculated as the difference between total depth and KOP (2501—144 MD), yields 2357 MD. Through trigonometric analysis using the cosine relationship (cos 30° = TVD/2357), the true vertical depth is determined to be 2041 MD, derived from the equation TVD = 2357 × ½√3. The well’s primary deviation parameter, characterized by an inclination angle (α) of 30 degrees, falls significantly below the critical threshold of 50 degrees, the maximum allowable deviation for effective broaching operations [63].

This geometric configuration, which maintains a 20-degree margin below the operational limit, facilitates optimal conditions for broaching tool deployment, scale removal efficiency, and overall operational success. The moderate deviation angle of the well facilitates effective tool weight transfer and mechanical advantage for scale removal while reducing the risks of tool binding and uneven load distribution.

4.5.3. Pre-Job Planning

Successful broaching operations require comprehensive well data analysis before execution. Essential documentation includes casing records, downhole surveys, PTS logs for flashpoints, wellhead schematics, and identification of problematic zones, including casing damage or debris [11,66]. Critical operational parameters such as flow rates and wellhead pressures must also be established. The success of the intervention heavily depends on effective communication and data sharing, between steamfield operators and slickline personnel, as this collaboration minimizes operational risks associated with the uncertain data.

4.5.4. Determination of Broaching Target Depths Based on Well Schematic Review

The well’s schematic analysis provides critical guidance for broaching operations by precisely identifying scale formation zones within specific casing sections. As illustrated in Figure 14, a detailed examination of scale deposition patterns against casing architecture enables accurate targeting of intervention depths. This systematic evaluation maps the scale accumulation location, facilitating proper tool selection and operational planning while accounting for casing specifications and potential mechanical constraints. The well schematic serves as the primary reference document, ensuring precise depth correlation and optimal execution of broaching operations.

4.5.5. Broaching Tools

Broaching equipment is categorized into two groups: surface and subsurface equipment, where surface equipment connects to subsurface equipment through wireline cable as shown in

Table 7. Broaching surface tools and its function [67].

Surface Equipment	Technical Function
Wireline Unit	Primary equipment carrier and operational base
Generator	Electrical power generation system
Compressor	Hydraulic system air supply unit
Control Room	Centralized operational command center
Wireline Drum	Cable spooling and storage system
Wireline	Primary tool deployment and retrieval cable
Measuring Wheel	Depth and velocity monitoring system
Down Sheave Wheel	Intermediate cable guidance system
Upper Wheel	Primary cable routing mechanism
Stuffing Box	Pressure containment and cable sealing system
Lubricator	Tool staging and pressure control chamber
BOP	Well control safety system
Flange	Wellhead connection interface

and

Table 8. Broaching subsurface tools and its function [67].

Subsurface Equipment	Technical Function
Wireline Cable	Primary connection and deployment cable system
Weight Bar	Downhole weight enhancement component
Jar	Mechanical impact generation mechanism
Spiral Catcher	Scale debris collection and containment system
Broaching Tool	Scale disintegration and removal apparatus

, and Figure 15 and Figure 16.

4.5.6. Design Specifications of Broaching String Assembly for Well X

Based on the broaching tool dimensions presented in

Table 9. Broaching tool dimensions [67].

Tool Specification	Length	Weight
Broaching 2.5″	60 cm	3.50 kg
Broaching 3.5″	60 cm	4.50 kg
Broaching 5.5″	60 cm	6.50 kg
Broaching 8.0″	60 cm	9.00 kg
Broaching 10.0″	60 cm	11.00 kg
Broaching 12.0″	60 cm	13.00 kg
Jar 3.0″	200 cm	7.25 kg
Weight Bar (Matches broaching size)	50 cm	10.00 kg
Spiral (Matches broaching size)	60 cm	3.50 kg

, the scale cleaning operation implements multiple broaching assembly configurations. The systematic design specifications for each assembly are presented in

Table 10. Selected broaching tool dimensions.

Assembly Specifications	3.5″ Assembly	5.5″ Assembly	8.0″ Assembly	10.0″ Assembly
Length Components
Broaching Tool	60 cm	60 cm	60 cm	60 cm
Jars	200 cm	200 cm	200 cm	200 cm
Weight Bar	50 cm	50 cm	50 cm	50 cm
Spiral/Catcher	60 cm	60 cm	60 cm	60 cm
Connections	20 cm	20 cm	20 cm	20 cm
Total Length	370 cm	370 cm	370 cm	370 cm
Mass Components
Broaching Tool	4.50 kg	6.50 kg	9.00 kg	11.00 kg
Jars	7.25 kg	7.25 kg	7.25 kg	7.25 kg
Weight Bar	10.00 kg	10.00 kg	10.00 kg	10.00 kg
Spiral/Catcher	3.50 kg	3.50 kg	3.50 kg	3.50 kg
Total Mass	25.25 kg	27.25 kg	29.25 kg	31.75 kg

.

As seen in Table 10, the broaching assembly analysis shows four configurations (88.9 mm (3.5 inches), 139.7 mm (5.5 inches), 203.2 mm (8.0 inches), and 254.0 mm (10.0 inches)), all maintaining a consistent total length of 3.7 m but varying in total mass. While component lengths remain identical across all assemblies, the total mass increases progressively from 25.25 kg in the 3.5″ assembly to 31.75 kg in the 10.0″ assembly, primarily due to the increasing weight of the broaching tool itself, while other component weights remain constant.

4.5.7. The Broaching Procedure

The broaching process starts by choosing the right tool size, usually based on previous well measurements. If no reliable past data exists, operators start with the smallest tool size for safety. The tool is lowered very slowly into the well to prevent damage and pinpoint the beginning of scale buildup. Once the tool touches the scale, operators record this depth and plan how quickly to work. The main cleaning work begins by using special jars (tools that create impact) to break down the scale bit by bit, like chipping away at the ice. How long this takes depends on how hard the scale is, how heavy the tools are, and how deep the blockage sits. After breaking through the first time, operators make several passes up and down to clean the area thoroughly before using a bigger tool size. This process repeats with increasingly larger tools until the well is cleaned to the appropriate size. Operators utilize additional cleaning methods, such as flowing the well or using scraper tools, to effectively remove all broken pieces of scale. The whole operation is carefully monitored by tracking tool depth and tension using different-sized tools (ranging from 88.9 mm (3.5 inches) up to 254.0 mm (10.0 inches)) until the planned depth is reached [11].

Figure 17 provides a graphical representation that illustrates the relationship between operational depth, tension measurements, and time duration during a standard broaching operation.

However, broaching carries higher risks compared to other methods due to its mechanical working principle and wireline usage. Here are the compatibility factors and potential impacts to consider when applying a broaching method to Well X:

• The scale column height in Well X is still manageable, making broaching operations relatively straightforward to implement.
• The inclination angle of Well X, at 30°, falls within the required limit of the broaching method, which is 50°. Therefore, this method is applicable to this well.
• The scale formation in Well X is relatively minimal, requiring a more economical method to avoid excessive costs. Broaching represents the most cost-effective scale stimulation method compared to other alternatives.
• High temperatures and potential tool-sticking incidents can pose risks of wireline breakage during scale cleaning operations.
• Complete scale removal may not be achievable in big-hole wells due to broaching tool diameter limitations. Additionally, the broaching tool’s cutting action might cause direct friction with the casing wall, potentially leading to casing leaks.

To evaluate the success of the broaching method, it is recommended to conduct caliper measurements after scale cleaning and review Well X’s production rate.

5. Conclusions

5.1. Summarys

This comprehensive study of scale formation and treatment in Well X at the Kamojang geothermal field has yielded several significant findings that contribute to our understanding of scale management in vapor-dominated systems. Through detailed investigation, scale formation was precisely identified at 900.74 m depth within the 339.7 mm (13-3/8 inches) production casing, characterized by a thickness of 252.7 mm (9.95 inches) and a column height of less than 1 m. Geochemical and XRD analyses definitively identified two distinct mineral phases: quartz (SiO₂) and magnetite (Fe₃O₄) as the primary scale components, with surface-based PHREEQC predictions indicating potential precipitation of goethite (FeO(OH)) and hematite (Fe₂O₃) under oxidizing conditions. The impact of scaling on well performance showed a distinct pattern—while steam production decreased by 8.9% from 31.5 to 28.71 tons/hour (2019–2022), the wellhead pressure declined by 2.1 bar from 18.6 to 16.5 bar (2020–2022), with most pressure reduction occurring after 2021, indicating the progressive nature of scale formation effects on well operations. The investigation included comprehensive well integrity testing using go-devil operations and sample catcher deployments, which provided crucial data for mapping scale formation zones and characterizing wellbore constrictions. After careful evaluation of various treatment options, the broaching method emerged as the most suitable solution, supported by three key factors: compatibility with the scale characteristics, an appropriate well inclination of 30° (well within the 50° limit), and superior economic viability at USD 42,690 compared to alternative methods ranging from USD 628,147 to USD 1,195,339. The economic analysis demonstrated exceptional returns, with the broaching intervention restoring steam production from 28.71 to 31.50 tons/hour. With a plant availability factor of 35% and steam price of USD 18.40/ton, this resulted in increased daily revenue of USD 431.22, yielding a monthly revenue gain of USD 12,936.63 and a rapid payback period of just 3.3 months. In contrast, conventional methods would require 4–10 years for cost recovery under similar conditions. This selection demonstrates the importance of balancing technical requirements with economic considerations in geothermal well maintenance, while the rapid return on investment validates broaching as an optimal scale treatment solution for vapor-dominated geothermal systems.

5.2. Recommendation

At PT. Pertamina Geothermal Energy, priorities should include systematic well integrity testing, post-treatment monitoring, and standardized broaching techniques catered to Kamojang field circumstances to improve scale management. It is necessary to use real-time tracking, a centralized database, and preventative maintenance programs in line with specialized equipment. Long-term sustainability and operational efficiency will be ensured through strategic budget allocation, research collaborations, internal knowledge building, and environmental assessments.