Experimental Verification of Reservoirs with Different Wettability Using an Oil–Water Relative Permeability Model

Round 1

Reviewer 1 Report

The work is of interest to the community and I think that it will benefit the readership. I have some minor comments:

1 Should the authors discuss more on their Kr results. What is kr characteristics obtained suggested? This will further validate or re-confirm the core study of the work.

2 There are a few wettability indices or characterizations. Should the authors also characterize some of those to report. Especially those are related to fluid flow properties.

Author Response

Dear reviewers:

    Thank you for your letter and the reviewers’comments concerning our manuscript entitled “Experimental Verification of Reservoirs with Different Wettability Using an Oil-Water Relative Permeability Model” (processes-1753890). Those comments are valuable and very helpful. We have read through comments carefully and have made corrections. Based on the instructions provided in your letter, we uploaded the file of the revised manuscript. Revisions in the text are shown in red. The responses to the reviewer's comments are marked in red and presented following. We uploaded the response file.Please see the attachment. 

Author Response File: Author Response.docx

Reviewer 2 Report

Nowadays literature background should reach over 30 articles, deeply studied.

Review is limited mainly to the literature of authors from China.

Please improve intruduction at first.

Author Response

Point 1: Comments and Suggestions for Authors

Nowadays literature background should reach over 30 articles, deeply studied.Review is limited mainly to the literature of authors from China.Please improve intruduction at first.

Response 1: Thank you for your suggestion. As suggested by reviewer, we expanded the scope of the literature reading, and deeply studied papers about relative permeability which were written by foreign authors. We try to find and cited papers that are highly relevant to our research. We have added the content of introduction to the manuscript on page 2. The number of references has been increased to 31 articles. The details of the additions as follows:

The experimental results show that the relative permeability calculation accuracy in the water phase is higher than that in the oil phase. Faruk Civan[8] described variation of porosity and permeability by scale dissolution and precipitation in porous media based on fractal attributes of the pores, the relationship between permeability and porosity conforming to Civan's power law flow units equation. Practical analytical solutionswere derived and verified by experimental data. Deviations of the empirically determined exponents of the pore‐to‐matrix volume ratio compared to the Kozeny‐Carman equation were due to the relative fractal dimensions of pore attributes of random porous media. He Yan [9] establishedthe relationship between relative permeability, water saturation and fractal dimension. Andersen[10-11] et al. derived relative permeability and capillary pressure functions from measurements of pressure drop and oil-production data in multirate water-injection tests.showed that the change of wettability toward a more-water-wet state can give an apparent EOR effect by reducing the end effects without there being any real reduction of the residual-oil saturation. Andersen’s reserch showed that the change of wettability toward a more-water-wet state can give an apparent EOR effect by reducing the end effects without there being any real reduction of the residual-oil saturation. Ma Jianbin[12] et al. deduced a formula for calculating rock permeability by employing resistivity based on Archie's formula and the famous Kozeny–Carman (KC) model[13], assuming that rock is spherical with uniform size. Using rock physical properties measured by a multi-parameter core scanner, the results were verified. The experimental results indicate that the proposed method can effectively characterise the relationship between rock resistivity and permeability. Tsakiroglou[14] et al. converted the electrical resistances to water saturations with the aid of the Archie equation for resistivity index. Both krw and krg are regarded as power functions of water, Caw, and gas, Cag, capillary numbers, the exponents of which are estimated with non-linear fitting to the experimental datasets.  The water saturation is insensitive to changes of water and gas capillary numbers and each relative permeability is affected by both water and gas capillary numbers. Liu Jiangtao[15] established a relationship model between relative permeability and normalised water saturation. Leili Moghadasi[16] et al. measured spatial and temporal dynamics of in-situ saturations along core samples directly through an X-Ray absorption technology. The latter rendered detailed distributions of (section-averaged) fluid flow phases through the medium, which can then be employed for the characterization of relative permeabilities. Bai Songtao [17] et al. studied the relationship between capillary pressure, nuclear magnetic resonance T2 spectrum, resistivity increase coefficient and relative permeability. Based on Fractal theory, they analyzed and deduced the exponential relationship between resistivity increase coefficient and relative permeability and verified it using data from rock physics experiments.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Thank you for following my remarks.