Diagenetic facies quantitative evaluation of low-permeability sandstone: A case study on Chang 82 reservoirs in the Zhenbei area, Ordos basin

Baoquan Ma,Qingdong Kong,Qinglin Bai,Shaochun Yang,Ya Wang,Hong Zhang,Chunting Song,Xidong Wang

doi:10.1177/0144598717738813

Abstract

Quantitative characterization of diagenetic facies has great significance for reservoir evaluation and prediction. In order to find out the method to evaluate diagenetic facies, the author took Chang 82 reservoir low-permeability sandstone in Zhenbei area of Ordos basin as research object and divided the reservoir into six types of diagenetic facies by analysis of casting thin section, scanning electron microscope, cathode luminescence, and physical property. According to 14 quantitative evaluating parameters which were related with petrology characteristic, diagenesis strength, pore structure, etc. quantitative evaluation of diagenetic facies of low-permeability sandstone reservoir was done by data envelopment analysis. The result showed that in the Chang 82 reservoir low-permeability sandstone in Zhenbei area of Ordos basin, quantitative representative indexes of diagenetic facies ranged from 0 to 1.00. Various diagenetic facies and their indexes had interval corresponding relation. The diagenetic facies of weak corrosion with chlorite mat and the diagenetic facies of corrosion of unstable components had the best reservoir quality. Their diagenetic facies indexes ranged from 0.66 to 1.00. The reservoir quality of the diagenetic facies filled with kaolinite was not as good as the former. The indexes ranged from 0.50 to 0.66. The diagenetic facies of quartz secondary enlargement and the diagenetic facies of clay mineral cementation replacement had poor reservoir quality. Their diagenetic facies indexes ranged from 0.30 to 0.40. The diagenetic facies of carbonate cementation had the poorest reservoir quality. It hardly possessed fluid storage capability. After comparing diagenetic facies indexes, absorption strength and remaining oil saturability, the perfect corresponding relation between quantitative evaluation results and reservoir quality could be verified.

Highlights

Diagenetic theory is the science about diagenetic environment, diagenetic condition, diagenesis, and its formative mechanism
Diagenesis theory is about high-permeability space distribution of different facies and lithologic bodies, which is the inner physical property and distribution features of reservoir and provides direct basis for prediction of high-quality reservoir and quantitative evaluation of advantageous reservoir space as well as confirm the inner bound of physical property distribution of sedimentary bodies
They were the diagenetic facies of quartz secondary enlargement, the diagenetic facies of filling with kaolinite, the diagenetic facies of carbonate cementation, the diagenetic facies of clay mineral cementation replacement, the diagenetic facies of weak corrosion with chlorite mat, and the diagenetic facies of corrosion of unstable components

Summary

Introduction

Diagenetic theory is the science about diagenetic environment, diagenetic condition, diagenesis, and its formative mechanism. Considering about their advantage and disadvantage and excluding former defects, such as assigning weight subjectively, different ranges of selected parameters, and complicated dimensionalized treatment, data envelopment analysis (DEA) was put forward to figure out index of diagenetic facies and described it quantitatively, quantitative evaluation of diagenetic facies was carried out on low-permeability sandstone reservoir in Chang 82 reservoir of Zhenbei area in Ordos basin.

Results

Conclusion