Oil & Gas Geology ›› 2019, Vol. 40 ›› Issue (3): 512-523.doi: 10.11743/ogg20190307

• Petroleum Geology • Previous Articles     Next Articles

Geological characteristics and effectiveness of the shale oil reservoir in Dongying sag

Liu Huimin1, Zhang Shun2, Bao Youshu2, Fang Zhengwei2, Yao Suping3, Wang Yong2   

  1. 1. Manage Center of Oil & Gas Exploration of Shengli Oilfield Branch Company, SINOPEC, Dongying, Shandong 257001, China;
    2. Exploration and Development Research Institute, Shengli Oilfield Branch Company, SINOPEC, Dongying, Shandong 257015, China;
    3. School of Earth Sciences and Engineering, Nanjing University, Nanjing, Jiangsu 210023
  • Received:2018-12-28 Revised:2019-03-28 Online:2019-06-28 Published:2019-04-26

Abstract: The reservoir space types of various sizes and their connection patterns of the Paleogene shale in Jiyang Depression were characterized through core observation,polarizing microscope and argon ion milling-scanning electron microscopy (SEM) analyses,and high pressure mercury injection,as well as small angle X ray scattering experiment; in addition,the lower limits of effective pore diameter and porosity were clarified according to data such as porosity and oil saturation.A spatial development and distribution model of shale reservoir in Dongying sag was established to predict the favorable reservoir facies belt through integrating thermal maturity (Ro) with the characteristics of lithofacies,formation pressure,and reservoir space (porosity and pore diameter).The results show that:(1) the pores of the shale reservoir in the study area are mainly intergranular pores,shrinkage pores in organic matter and clay minerals,and intercrystalline pores in carbonate,all of which are connected through a three-level pore-fracture network; (2) the intraparticle pores in clay minerals and intercrystalline pores in carbonate are the most effective pores with the highest contribution to the total porosity,averaging at 50% to 70%,followed by clay shrinkage cracks and tension fissure; (3) the lower limit of pore diameter for shale oil occurrence,the minimum pore diameter for free oil occurrence,and the threshold pore diameter of free oil enrichment are 5nm,10nm and 30mm,respectively; (4) the laminated shale rich in organic matter and carbonate minerals is the highest in total porosity,pore connectivity,and contribution of pores favorable for free oil storage to porosity,so it is a preferential lithofacies; (5) the development and distribution characteristics of shale reservoir space are controlled by the lithofacies type,diagenetic stage,formation pressure and fracture development degree,all of which also serve as important factors for the evaluation of shale oil sweet spots; the prediction of favorable reservoir facies belt is to identify laminated organic-rich shale with relatively higher thermal maturity,highly-developed fracture and high formation pressure under the guidance of graded evaluation scheme.

Key words: shale oil, reservoir space, pore diameter, lithofacies, favorable reservoir facies belt, Shahejie Formation, Dongying sag, Jiyang Depression

CLC Number: