缝洞型碳酸盐岩储层循缝找洞压裂技术

Fracturing technology of searching for vugs along fractures in fractured-vuggy carbonate reservoirs

赵海洋 刘志远 唐旭海 李新勇 耿宇迪 张俊江

ZHAO Haiyang LIU Zhiyuan TANG Xuhai LI Xinyong GENG Yudi ZHANG Junjiang

中国石化西北油田分公司石油工程技术研究院 中国石化缝洞型油藏提高采收率重点实验室 武汉大学土木建筑工程学院

Research Institute of Petroleum Engineering, SINOPEC Northwest Oilfield Company, Urumqi 830011, Xinjiang, China SINOPEC Key Laboratory of Enhanced Recovery of Fracture-Cave Reservoir, Urumqi 830011, Xinjiang, China School of Civil Construction Engineering, Wuhan University, Wuhan 430072, Hubei, China

深层及超深层缝洞型碳酸盐岩溶洞是油气的主要储集空间，压裂裂缝受地应力控制主要沿水平最大地应力方向扩展，并沟通该方向上的溶洞，其他方向的溶洞无法与井眼连通，导致井周储量动用程度低。根据碳酸盐岩储层伴生缝洞发育特点，提出循缝找洞的储层改造思想，即压裂过程中通过控制泵注压力注入流体，流体遵循原生天然裂缝的展布形态进行流动，形成相互连通的人工裂缝通道，沟通不同方向的多个溶洞，减少地应力对压裂裂缝形态的影响。通过构建含天然裂缝网络和溶洞的模型，采用TOUGH2-AiFrac耦合求解算法，研究天然裂缝数量、走向对压裂裂缝沟通溶洞的影响规律。结果显示天然裂缝走向对压裂裂缝扩展轨迹有较大影响，天然裂缝走向偏向溶洞有利于压裂裂缝沟通溶洞；不同数量、不同走向的天然裂缝网络能够有效连通不同方向的多个溶洞，说明能通过循缝找洞实现井周储量的高效动用。以循缝找洞思想为指导形成的技术方案现场应用85井次，2020年增加原油产量16.12万t，为深层及超深层缝洞型碳酸盐岩油气藏的改造增产提供了方向。

Deep and ultradeep fractured-vuggy carbonate vugs are the main oil and gas reservoir spaces. Under the control of in-situ stress, hydraulic fractures propagate mainly along the direction of the maximum horizontal stress to connect the vugs in this direction, while the vugs in the other directions cannot be connected with the boreholes, so the circumferential reserve producing degree is low. The reservoir stimulation idea of searching for vugs along fractures was put forward according to the development characteristics of the associated fractures and vugs of carbonate reservoirs. That is to inject the fluid by controlling the pumping pressure in the process of fracturing, so that the fluid can flow along the distribution forms of primary natural fractures to form interconnected hydraulic fracture pathways to connect multiple vugs in different directions and reduce the influences of in-situ stress on the morphology of hydraulic fractures. Then, the influential laws of the quantity and strike of natural fractures on the connection of vugs by hydraulic fractures were studied by using the TOUGH2-AiFrac coupling algorithm and constructing the model containing natural fracture network and vug. It is indicated that the strike of natural fractures has greater influence on the propagation tracks of hydraulic fractures, and when the strike of natural fractures is deviated towards vugs, it is favorable for the hydraulic fractures to connect vugs. In addition, natural fracture networks of different quantities and strikes can effectively connect multiple vugs in different directions, indicating that efficient production of circumferential reserves can be realized by searching for vugs along fractures. The technical scheme formulated according to the idea of searching for vugs along fractures has been applied on site 85 well times and the incremental oil in 2020 is 16.12×10 t. The research results provide the direction for the stimulation of deep and ultradeep fractured-vuggy carbonate oil and gas reservoirs.

10.13639/j.odpt.2021.01.014