Oil & Gas Geology ›› 2022, Vol. 43 ›› Issue (5): 1238-1248.doi: 10.11743/ogg20220518

• Methods and Technologies • Previous Articles     Next Articles

Application of an integrated geology-reservoir engineering approach to shale oil development in Ansai area, Ordos Basin

Chenglin Liu1,2(), Xinju Liu3, Hongjun Zhang4, Liyong Fan5, Xiya Yang1,2,4, Qibiao Zang1,2, Bo Dai4, Yue Meng4, Hongliang Huo1,2, Fang Wang6   

  1. 1.State Key Laboratory of Petroleum Resources and Prospecting,China University of Petroleum (Beijing),Beijing 102249,China
    2.College of Geosciences,China University of Petroleum (Beijing),Beijing 102249,China
    3.Research Institute of Exploration and Development,Changqing Oilfield Company,PetroChina,Xi'an,Shaanxi 710018,China
    4.No. 1 Oil Production Plant,Changqing Oilfield Company,PetroChina,Shaanxi,Yan’an 716009,China
    5.National Engineering Laboratory for Exploration and Development of Low-Permeability Oil & Gas Fields,Changqing Oilfield Company,PetroChina,Shaanxi,Xi’an 710018,China
    6.Exploration and Development Research Institute,Huabei Oil Company,PetroChina,Renqiu,Hebei 062550,China
  • Received:2022-01-05 Revised:2022-07-08 Online:2022-10-01 Published:2022-09-02

Abstract:

Shale oil is a hot spot for petroleum exploration and development over the world. Given its unique geological features, enrichment mechanisms, and development conditions, shale oil is desirable for an integration of geology and reservoir engineering. A variety of technical methods such as field geological survey, core observation and sampling, logging data interpretation, geological and engineering parameter analysis and testing, are applied to geological evaluation of shale oil with focuses on reservoir lithology, thickness, porosity, permeability, oil saturation, fracture development and selection of sweet spots; while in terms of reservoir engineering evaluation, we propose a development method and parameters appropriate to the shale oil in Ansai area regarding the geological characteristics of sweet spots. The main understandings obtained are as follows. First, the 7th member of the Triassic Yanchang Formation (Chang 7 Member) in Ansai area, Ordos Basin is typical of continental shale oil mainly of delta front and semi-deep lacustrine subfacies. The tight sandstones therein mainly belong to reservoirs with low to ultra-low porosity and ultra-low permeability or non-reservoirs. In light of geological and geomechanical parameters, the reservoirs can be classified into 4 types from good to poor, including Type Ⅰ, Type Ⅱ, Type Ⅲ and Type Ⅳ, with the first two types being targets of sweet spots. Second, the flow of shale oil in reservoirs of the Chang 7 Member are driven by reservoir fluid, rocks'elastic expansion and gas dissolution, while the potential of energy supplement via gas injection is limited. For Type Ⅰ reservoirs selected by geological evaluation, the nine-point, seven-point or staggered horizontal well patterns are used for quasi-natural depletion, while the seven-point or five-point horizontal well patterns are used for development of Type Ⅱ reservoirs. Third, the typical horizontal wells in the Chang 7 Member is of low initial production with a high decline rate at the initial stage, but the decline rate gradually reduces in the later stages. Moreover, it features a long production cycle with a relatively stable production.

Key words: production, horizontal well, geology-reservoir engineering integration, tight sandstone, shale oil, Chang 7 Member, Ansai area, Ordos Basin

CLC Number: