塔河油田胶束软隔挡控缝高酸压方法研究

Study on the acid fracturing method for fracture height control based on micellar soft barrier suitable for the Tahe Oilfield

宋志峰 张照阳 毛金成

SONG Zhifeng ZHANG Zhaoyang MAO Jincheng

中国石化西北油田分公司石油工程技术研究院 西南石油大学油气藏地质及开发工程国家重点实验室

Research Institute of Petroleum Engineering, SINOPEC Northwest Oilfield Company, Urumqi 830001, Xinjiang, China State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, Sichuan, China

塔河油田奥陶系碳酸盐岩油藏部分区块底水发育，储层垂向应力差小且高角度裂缝发育，酸压过程中缝高易失控沟通水层。随着酸压避水高度逐年减小，控缝高酸压难度增大，因此有必要开展控缝高酸压方法研究，以控制裂缝高延伸、提升底水型储层改造效果。通过揭示人工隔层控制裂缝高度延伸本质，分析胶束软隔挡控缝机理，提出了胶束软隔挡控缝高方法，实验结果表明：黏弹性胶束隔挡材料质量分数为5%时，120 ℃下胶束溶液剪切黏度保持在430 mPa · s以上，有利于增大裂缝垂向应力差；黏弹性胶束隔挡材料隔挡强度达到12.2 MPa，对于塔河油田碳酸盐岩垂向应力差小(≤2 MPa)地层，可形成较强的柔性隔挡层，控制裂缝垂向延伸；结合塔河油田酸压工艺特点，在注酸液过程中，胶束液对近井筒裂缝实现隔挡屏蔽，酸液继续指进，在裂缝深部随着酸液的冲刷以及裂缝的延伸，隔挡材料质量浓度减小，酸液对裂缝酸蚀作用变强，实现在近井筒阻缓裂缝高度过度延伸、深部形成强刻蚀高导流裂缝通道。

In the Ordovician carbonate oil reservoir of the Tahe Oilfield, bottom water is developed in some blocks, the vertical stress difference of reservoir is small and high-angle fractures are developed, so in the process of acid fracturing, the fracture height tends to be out of control and connect the water layers. And as the water avoidance height of acid fracturing decreases year after year, the fracture height control acid fracturing gets more and more difficult. Therefore, it is necessary to study the fracture height control acid fracturing method so as to control the propagation of fracture height and improve the stimulation effect of bottom-water reservoirs. In this paper, the essence of artificial barrier controlling the propagation of fracture height was revealed, the mechanism of micellar soft barrier was analyzed, and the method to control the fracture height using micellar soft barrier was proposed. It is experimentally indicated that when the mass fraction of viscoelastic micellar barrier material is 5%, keeping the shear viscosity of micellar solution above 430 mPa · s at 120 ℃ is favorable for the increase of the vertical stress difference of fracture. When the barrier strength of viscoelastic micellar barrier material reaches 12.2 MPa, stronger flexible barrier can be formed in the carbonate reservoirs with small vertical stress difference (≤2 MPa) in the Tahe Oilfield to control the vertical propagation of fractures. Combined with the technological characteristics of acid fracturing in the Tahe Oilfield, the micellar solution acts as the barrier to the fractures near the wellbore in the process of acid injection. As acid fingering continues, with the erosion of acid and the propagation of fracture, the mass concentration of barrier material declines and the erosion effect of acid on the fracture increases in the deep part of the fracture. In this way, the excessive propagation of fracture height near the wellbore is hindered, and strong-erosion and high-conductivity fracture channels are formed in the deep part.

10.13639/j.odpt.2019.03.019