夹层型致密储层密切割压裂多裂缝同步扩展机制

Multi-fracture synchronous propagation mechanism of dense cutting fracturing in interlayer tight reservoir

张军 余前港 李玉伟 李玮 严茂森 白明涛 王阳

东北石油大学石油工程学院，黑龙江 大庆 163318 辽宁大学环境学院，辽宁 沈阳 110036 中国石油大庆油田有限责任公司井下作业分公司，黑龙江 大庆 163318 中国石油大庆油田有限责任公司第二采油厂，黑龙江 大庆 163000

School of Petroleum Engineering, Northeast Petroleum University, Daqing 163318, China School of Environment, Liaoning University, Shenyang 110036, China Downhole Operation Branch, Daqing Oilfield Co., Ltd., PetroChina, Daqing 163318, China No. 2 Oil Production Plant, Daqing Oilfield Co., Ltd., PetroChina, Daqing 163000, China

松辽盆地夹层型致密储层天然裂缝不发育且储层脆性较低，复杂缝网难以形成，同时储层纵向上砂层发育、泥岩夹层薄、隔层遮挡能力弱，裂缝纵向扩展受限，储层改造效果较差。针对以上问题，利用三维晶格方法建立夹层型致密砂岩储层多裂缝扩展模型，模拟不同地质因素和工程因素条件下的多裂缝同步扩展规律。结果表明：垂向应力差、夹层弹性模量以及界面强度与多裂缝纵向扩展能力正相关；15.0 m的簇间距既能保证多裂缝在纵向上穿透夹层沟通产层，又能保证多裂缝在横向上的充分扩展。相比8，12 m3/min的泵注排量所形成的多裂缝，虽然总长度略微减小，但能够保证3簇裂缝都有比较理想的纵向扩展能力，从而提高了裂缝沟通面积。压裂液黏度与裂缝纵向扩展能力正相关，与横向扩展能力负相关。因此，建议现场前期采用高黏度压裂液（21 mPa·s以上），促使裂缝垂向扩展，后期采用低黏度压裂液（1 mPa·s左右）使多裂缝尽可能向远端扩展，提高压裂效果。

The interlayer tight reservoir in Songliao Basin is characterized by undeveloped natural fractures and low reservoir brittleness, so it is difficult to form a complex fracture network. And the sandstone is developed vertically in the reservoir, mudstone interlayer is thin, and the barrier shielding ability is weak. The vertical expansion of fractures is limited, so the effect of reservoir reconstruction is poor. In view of these problems, the multi-fracture propagation model of interlayer tight sandstone reservoir is established by using the three-dimensional lattice method, and the multi-fracture synchronous propagation law under different geological factors and engineering factors is simulated. The results show that the vertical stress difference, interlayer elastic modulus and interface strength are positively related to the vertical propagation ability of multi-fracture. The cluster spacing of 15 m not only ensures that the multi-fractures penetrate the interlayer in the vertical direction to communicate with multiple pay zones, but also ensures the full expansion in the transverse direction. Compared to the multi-fractures formed by 8 and 12 m3/min pumping displacement, although the total length is slightly reduced, it can ensure that the three clusters of artificial fractures have ideal vertical expansion capacity, thus improving the connected fracture area. The viscosity of fracturing fluid is positively correlated with the vertical propagation ability, but negatively correlated with the lateral propagation ability. Therefore, it is recommended to use high viscosity fracturing fluid (above 21 mPa·s) at the early stage to promote the fractures expanding vertically, and use low viscosity fracturing fluid (about 1mPa·s) at the later stage to make multi-fractures expand to the far end as much as possible and improve the fracturing effect.

10.6056/dkyqt202303016