构造运动对扎格罗斯前陆盆地白垩系碳酸盐岩储层的影响——以Y油田为例

Influence of tectonic movement on Cretaceous carbonate reservoirs in the Zagros Foreland Basin: A case study of Y oilfield

以扎格罗斯前陆盆地东北部的Y油田白垩系碳酸盐岩储层为例,利用岩心、薄片样品、成像测井和三维地震资料,探讨构造运动对碳酸盐岩储层成岩作用、裂缝发育以及热液流体活动的影响。研究表明,晚白垩纪至全新世的构造运动对Y油田白垩系碳酸盐岩储层影响最重要。构造运动期间地壳抬升,地层遭受剥蚀、风化等作用从而发育不整合面,不整合面以下的储层受溶蚀作用改造显著。而阿拉伯板块与欧亚板块碰撞发生的褶皱作用和逆冲作用在储层内部生成大量裂缝,裂缝的密度和位置受褶皱、断层以及岩性的共同影响。裂缝主要发育在褶皱的轴部和翼的尾部以及断裂附近,白云岩的裂缝密度明显大于灰岩的。构造运动还控制了Y油田内热液流体活动,断层是热液流体进入Y油田的主要通道,热液白云化作用主要发生在靠近断裂或裂缝带的地堑内。探讨构造运动对碳酸盐岩储层的影响,有利于预测定位研究区的优质储层,优化油田的生产部署。

On the basis of drilling cores ,thin sections ,imaging logging and 3D seismic data,the study discusses the effects of tectonic movement on diagenesis,fractures development and hydrothermal fluid activities of carbonate reservoirs in Y oilfield of the northeastern Zagros Foreland Basin. Tectonic movements from the late Cretaceous to the Holocene have most significant effect on the Cretaceous carbonate reservoirs in Y oilfield. During this period, because of compressional uplift, target strata were heavily eroded and weathered, which leads to development of an unconformity surface. Reservoirs below the surface suffered from severe dissolution. With the collision between Arabian plate and the Eurasian plate, and resultant folding and thrusting induced formation of fractures within reservoirs. Density and location of fractures were influenced by the intensity of folding and faulting, but also related to lithology. Fractures were mainly developed in the area around faults, and along fold axis or the lower end of fold limbs. In terms of lithology ,fracture density in dolomite is obviously higher than that in limestone. Tectonic movements also controlled the hydrothermal fluid activities in Y oilfield. The faults are the main pathways of hydrothermal fluid into Y oilfield. Hydrothermal dolomitization occurred in grabens close to faults or fracture zones. Discussing the influence of tectonic movements on carbonate reservoir is beneficial for predicting and locating high-quality reservoirs in the study area, and optimizing production deployment of the oilfield.