Multi-Phase Flow in Wellbore and Machine Learning Optimization Method

As the wellbore pressure falls below the bubble point pressure, the light components in the oil phase are liberated, forming additional vapor, and the single-phase flow becomes a gas–liquid two-phase flow. However, most studies simplify the multiphase flow to a single-phase flow to study asphaltene deposition in wellbores. This assumption under multiphase conditions may lead to inaccurate prediction results and a substantial economic and operational burden for the oil and gas industry. Therefore, it is crucial to predict the deposition rate of asphaltene in a multiphase flow to assist in minimizing this issue. To do so, the volume of fluid coupling level-set (VOSET) model was used to obtain the flow pattern (bubble, slug, churn, and annular) in the current work. In the next step, the VOSET + k-ε turbulent + DPM models were used to simulate asphaltene deposition in a multiphase flow. Finally, the effects of different parameters, such as the gas superficial velocity, liquid superficial velocity, particle diameter, interfacial tension, viscosity, and average deposition rate, were investigated. The findings revealed that the maximum average deposition rate of asphaltene particles in a bubble flow is 1.35, 1.62, and 2 times that of a slug flow, churning flow, and annular mist flow, respectively. As the apparent velocity of the gas phase escalates from 0.5 m/s to 4 m/s, the average deposition rate experiences an increase of 82%. Similarly, when the apparent velocity of the liquid phase rises from 1 m/s to 5 m/s, the average deposition rate is amplified by a factor of 2.1. An increase in particle diameter from 50 μm to 400 μm results in a 27% increase in the average deposition rate. When the oil–gas interfacial tension is augmented from 0.02 n/m to 0.1 n/m, the average deposition rate witnesses an 18% increase. Furthermore, an increase in crude oil viscosity from 0.012 mPa·s to 0.06 mPa·s leads to a 34% increase in the average deposition rate. These research outcomes contribute to a deeper understanding of the asphaltene deposition problem under multiphase flow conditions and offer fresh perspectives on the asphaltene deposition issue in the oil and gas industry. Full article

Unconventional well technology is often used as one of the most important means to reduce costs and increase efficiency in oil fields. There are many methods for unconventional well type optimization, but there are relatively few studies on whether the well type is suitable for the reservoir. In this paper, a method for matching unconventional wells and reservoirs is established. In our method, we first simplify the reservoir and choose initial suitable well types based on experience and then use a semi-analytical model to calculate the production rate in different producing sections. After that, we define some parameters to evaluate the matching degree of well types and reservoirs. Finally, we determine whether these well types are suitable for the reservoir based on these parameters. At the end of the paper, we apply the method to a specific case. The result shows that a stepped well is suitable for exploiting thin interbed reservoirs, but it is necessary that the permeability and fluid viscosity in different layers are within a certain range, and the shape of the stepped well is also limited. This paper gives a specific value for this range and limitation. The method for matching unconventional wells and reservoirs proposed in this paper is helpful for guiding the selection of unconventional well types before drilling. Full article

With the advancement of completion technology for horizontal wells in bottom water reservoirs, Autonomous Inflow Control Devices (AICDs), which have achieved good results in recent years, have been widely used in the oil fields of the eastern South China Sea. Although some mathematical methods can be used to predict the production performance of horizontal wells, there is no dynamic prediction method for the production performance of horizontal wells completed with AICDs. In this work, a mathematical model of porous flow in the reservoir, nozzle flow in the AICD, and pipe flow in the horizontal well is established, and then a new model is presented for predicting the dynamic performance of horizontal wells completed with AICDs in bottom water reservoirs. The new coupling model is compared with two horizontal wells completed with AICDs in the bottom water reservoirs of the eastern South China Sea, and the results indicate that the accuracy of the new model is sufficiently high to provide theoretical support for the further prediction of horizontal wells in the eastern South China Sea. Full article