渤中凹陷深层储层裂隙发育程度实验研究

Experiment Study on Microfracturing of Deep Reservoirs in the Bozhong Sag,Bohai Bay Basin

渤中凹陷作为渤海深层油气勘探最现实的有利区,其资源潜力和勘探前景有待得到进一步验证。由于深部潜山储层地质情况复杂,岩性繁多且差异明显,对深部有效储层类型及分布的研究是渤中地区深层勘探的关键。本文通过对渤中地区太古宇二长花岗岩、片麻状花岗岩、花岗质片麻岩、斜长角闪岩、古生界灰岩以及中生界安山岩6种潜山代表性岩石,开展张应力和压应力作用下的裂隙发育程度实验,观测在相同加载条件下不同岩性的微裂隙发育数、事件率等特征以及微裂隙时空分布,分析不同岩性样品裂缝发育能力及空间展布。实验结果表明:6种岩石储层在张应力和压应力条件下,均有一定规模的微裂隙产生,但在同一应力条件下其微裂隙发育累计及时空分布差异明显。其中,太古宇变质岩的内部裂隙发育程度高于古生界灰岩以及中生界安山岩储层。因此,岩性是控制储层裂缝发育的基础,相同的构造应力下太古界变质岩储层裂缝发育程度最高、储集能力最强。

The Bozhong Sag is the most favorable area for deep oil and gas exploration in the Bohai Bay Basin,and its resource potential and exploration prospects have been verified.The geological conditions of deep hill-buried reservoirs are very complex,with highly varied lithology.The information on the types and distribution of deep effective reservoirs is the key to deep exploration in the Bozhong Sag.In this paper,microfracturing behaviors of six typical rocks in the buried hills in the Bozhong Sag,including Archean monzogranite,gneissic granodiorite,granitic gneiss,amphibolite,Paleozoic limestone and Mesozoic andesite,are investigated experimentally under tensile stress and compressive stress,respectively.The development ability and spatial distribution of the microfractures in different rock samples are analyzed.The experimental results show that under tensile stress and compressive stress,there are certain scale of microfractures in six type of rock reservoirs,but under the same stress,the accumulation and spatial-temporal distribution of microfractures are obviously different.The internal microfractures in the Archean metamorphic rocks are more intensive than those in the Paleozoic limestone and the Mesozoic andesite reservoir.Lithology basically controls the development of reservoir fracture.Under the same tectonic stress,the Archean metamorphic rock reservoir has the highest fracture degree and the strongest reservoir capacity.