CO2埋存过程中断层水力破裂机制及稳定性定量评价

The objective of geological storage of CO2 in the abandoned reservoirs, brine formations or coal formations is to keep it not to escape in hundreds or thousands of years. So we need to make correct evaluation of its escapement pathway. Fault is one of the important way of the escapement of CO2 and lack of effective evaluation method so far.This project make Daqingzijing structure in Jilin oilfield as the main anatomy object. We will build geomechanical model which considered multifactor fault hydraulic fracture based on basic principle of hydraulic fracture. We obtain actual core data from core microstructure and outcrops, and obtain evaluation parameters by measuring technique of cohesion and tensile strength of fault rock and crustal stress, ultimately, we carried out quantitative evaluation of fault stability and make determination of the stability pressure.We made outcrop faults as the anatomy object to test the shale content of the fault zone and build its prediction model. Based on the shale content and pressure difference across fault surface, we established the quantitative relationship between shale content and nowaday fault sealing capacity. Taking the difference of interfacial tension between CO2 and CH4 or brine, oil and brine into account, we have build quantitative evaluation method of the nowaday fault sealing capacity of CO2 storage and determine the threshold pressure(express as increment of pore fluid pressure). Based on the relationship of stability pressure and threshold pressure to make constraints of CO2 injection rate and injection pressure, and then make the quantitative evaluation of fault escapement to come true.

CO2埋存在地下废弃油藏、卤水层或煤层中的目标是几百或几千年而不逸散，因此需要对逃逸途径做出正确评价。断裂是CO2潜在的重要逸散途径之一，目前缺少有效的评价方法。本项目以吉林油田大情字井构造为重点解剖对象，依据水力破裂基本原理，构建考虑多因素的断层水力破裂的地质力学模型，从岩心微构造和野外露头断裂获取实际岩心资料，利用断层岩内聚力和抗张强度以及地应力测试技术获取评价参数，实现断层稳定性定量评价并确定稳定压力。以野外露头断裂带为解剖对象，测试断裂带泥质含量，建立断裂带泥质含量预测模型，依据泥质含量和断裂支撑压力差关系，建立泥质含量和断层现今封闭能力之间的定量关系，考虑CO2-卤水和CH4、油-卤水界面张力差异，建立CO2埋存过程中断层现今封闭能力定量评价方法并确定突破压力（以孔隙流体压力增量表达）。依据稳定压力和突破压力关系，约束CO2注入量和注入压力，实现断层逃逸的定量评价。

CO2 埋存在地下废弃油藏、卤水层或煤层中的目标是几百或几千年而不逸散，因此需要对逃逸途径做出正确评价。断裂是CO2 潜在的重要逸散途径之一，目前缺少有效的评价方法。本项目以吉林油田大情字井构造为重点解剖对象，依据水力破裂基本原理，构建考虑多因素的断层水力破裂的地质力学模型，从岩心微构造和野外露头断裂获取实际岩心资料，利用断层岩内聚力和抗张强度以及地应力测试技术获取评价参数，实现断层稳定性定量评价并确定稳定压力。以野外露头断裂带为解剖对象，测试断裂带泥质含量，建立断裂带泥质含量预测模型，依据泥质含量和断裂支撑压力差关系，建立泥质含量和断层现今封闭能力之间的定量关系，考虑CO2-卤水和CH4、油-卤水界面张力差异，建立CO2 埋存过程中断层现今封闭能力定量评价方法并确定突破压力（以孔隙流体压力增量表达）。依据稳定压力和突破压力关系，约束CO2 注入量和注入压力，实现断层逃逸的定量评价。