玛湖凹陷砂砾岩储层岩石力学特征与压裂对策研究

Study on Rock Mechanic Characteristics and Fracturing Countermeasures of Glutenite Reservoirs in Mahu Depression

摘要: 玛湖凹陷百口泉组砂砾岩油藏储量大，但储层孔渗差、单井产量低、综合开采成本高，“水平井 + 压裂”是开发该类储层的有效措施，由于对其地应力和岩石力学特征认识不清严重制约了压裂改造的有效性。通过室内声学、力学试验发现玛湖凹陷百口泉组砂砾岩储层存在两向地应力差高、最小水平主地应力高、岩心弹性模量小、硬度低等特点，压裂改造无法形成复杂缝网，推荐采用密切割分段体积压裂工艺增大改造体积、采用前置液挤酸预处理结合小粒径段塞方式减少压裂加砂施工难度、适当加大支撑剂铺设厚度以及近井地带使用滑溜水造长复杂缝等措施提高改造效果。结合以上压裂施工建议，2015年底顺利完成了对试验井MaHW1325井22段体积压裂，入井压裂液23,700 m³、支撑剂1702 m³，截止到2017年8月下旬MaHW1325井累计生产528 d，累计产油12,786.8 t，平均日产油24.2 t，生产效果好，说明压裂改造方案成功，在该区块具有极高推广价值。

Abstract: In the glutenite reservoirs of Baikouquan Formation in Mahu Depression, reserves were high, but the porosity and permeability were poor, and single well production was low with high cost, so horizontal well + fracturing was the effective development measure for the reservoirs. Because of unclear understanding of the in-situ stress and rock mechanic characters, the effect of fracturing and reconstruction was constrained. The laboratory acoustic and mechanical tests revealed that there existed the characters of high stress difference in two directions, high minimum horizontal principal stress, small elastic modulus of rock cores and low hardness, fracturing reconstruction could not produce complex fracture networks. Therefore, it was recommended to use dense cut sectional volume fracturing for expanding the fracturing volume, pretreatment with prepaid-fluid acid squeezing combined with small diameter slugs for reducing the difficulty in fracturing and sand adding operation, rationally enhancing the proppant thickness and using slip water to produce long and complex fractures for the purpose of improving the efficiency of fracturing reconstruction. The volume fracturing was carried out in 22 well sections for Well MaHW1325, and 23,700 m³ fracturing fluid and 1702 m³ proppant were used for fracturing operations by the end of 2015. By the end of late August, 2017, Well MaHW1325 produces for 528 d with accumulated oil production of 12,786.8 t, and the average daily oil production is 24.2 t, and good effect is obtained in production. It indicates that the fracturing reconstruction program is successful. It has a high value for popularization in the block.