摘要
以鄂尔多斯盆地榆林和大吉地区深部煤岩气为研究对象,选取石炭系本溪组不同割理/裂缝发育程度的全直径煤岩样品,开展煤岩气全生命周期衰竭开发物理模拟和同位素监测实验,基于实验结果构建割理/裂缝-基质孔耦合的双重介质同位素分馏模型,并建立游离气产出规律评价方法,揭示深部煤岩气开发过程碳同位素分馏机理及吸附气、游离气产出特征。研究表明:深部煤岩气开发过程中碳同位素存在“稳定(Ⅰ)→变轻(Ⅱ)→变重(Ⅲ)”的3阶段分馏特征,第Ⅲ阶段边界压力的快速降低会导致同位素值出现“快速变轻后继续变重”的波动特征,呈现游离气优先动用、吸附气长期供给的特点;同位素分馏模型能够较好地同时拟合实测气体压力、累产气量和产出气δ^(13)C_(1)值,煤岩样品同位素分馏前两阶段累产气以游离气为主,在压降缓慢的生产中后期通过阶段式逐级控压开采方式能有效提高气体采收程度;吸附气动用主要受控于岩石的吸附能力和次级渗流通道,在生产后期有效提高吸附气的动用程度仍是深部煤岩气保持稳产和提高采收率的关键。
Taking deep coal-rock gas in the Yulin and Daning-Jixian areas of the Ordos Basin as the research object,full-diameter coal rock samples with different cleat/fracture development degrees from the Carboniferous Benxi Formation were selected to conduct physical simulation and isotope monitoring experiments of the full-life-cycle depletion development of coal-rock gas.Based on the experimental results,a dual-medium carbon isotope fractionation(CIF)model coupling cleats/fractures and matrix pores was constructed,and an evaluation method for free gas production patterns was established to elucidate the carbon isotope fractionation mechanism and adsorbed/free gas production characteristic during deep coal-rock gas development.The results show that the deep coal-rock gas development process exhibits a three-stage carbon isotope fractionation pattern:“Stable(I)→Decrease(Ⅱ)→Increase(Ⅲ)”.A rapid decline in boundary pressure in stageⅢleads to fluctuations in isotope value,characterized by a“rapid decrease followed by continued increase”,with free gas being produced first and long-term supply of adsorbed gas.The CIF model can effectively match measured gas pressure,cumulative gas production,and δ^(13)C_(1) value of produced gas.During the first two stages of isotope fractionation,free gas dominated cumulative production.During the mid-late stages of slow depletion production,staged pressure control development method can effectively increase the gas recovery.The production of adsorbed gas is primarily controlled by the rock’s adsorption capacity and the presence of secondary flow channels.Effectively enhancing the recovery of adsorbed gas during the late stage remains crucial for maintaining stable production and improving ultimate recovery factor of deep coal-rock gas.
作者
端祥刚
李文镖
胡志明
王峻
赵群
夏勇辉
马占荣
许莹莹
孙明岩
DUAN Xianggang;LI Wenbiao;HU Zhiming;WANG Jun;ZHAO Qun;XIA Yonghui;MA Zhanrong;XU Yingying;SUN Mingyan(PetroChina Research Institute of Petroleum Exploration&Development,Beijing 100083,China;Key Laboratory of Coal-rock Gas,CNPC,Beijing 100083,China;Sanya Offshore Oil&Gas Research Institute,Northeast Petroleum University,Sanya 572025,China;School of Geosciences,China University of Petroleum(East China),Qingdao 266580,China;PetroChina Changqing Oilfield Company,Xi’an 710018,China)
出处
《石油勘探与开发》
北大核心
2025年第5期1166-1179,共14页
Petroleum Exploration and Development
基金
国家自然科学基金青年基金(42302170)
中国石油天然气集团有限公司科技创新基金(2022DQ02-0104)
中国石油勘探开发研究院开放课题基金(2024-KFKT-31)。
关键词
深部煤岩气
同位素分馏
物理模拟实验
吸附气
游离气
气体产出比例
deep coal-rock gas
isotope fractionation
physical simulation experiment
adsorbed gas
free gas
gas production ratio
