松辽盆地中生代火山岩优质储层控制因素及分布预测

Controlling Factors and Distribution Prediction of High-quality Reservoir of Mesozoic Volcanic Rocks in Songliao Basin

中生代火山岩是松辽盆地深层天然气藏的主要储层。综合研究认为松辽盆地中生代火山岩优质储层的形成受控于岩性、岩相、裂缝及成岩作用,裂缝发育的酸性爆发相或溢流相顶部是火山岩优质储层主要发育区带。火山岩岩性控制孔隙的发育程度,是优质储层形成的基础,通过不同岩性的物性特征对比研究,提出酸性火山岩为深层优势岩性。一个完整的火山机构从中心向边部依次发育火山通道相、溢流相、侵出相、爆发相、火山沉积相,通过已钻井资料对比分析发现,岩相控制火山机构内优质储层的分布,近火山口的爆发相、溢流相上部亚相为有利的相带。裂缝是深部流体运移的重要通道,可以改善渗透条件,促使次生孔隙发育,是高产气藏形成的关键,高角度裂缝和溶蚀孔隙组合带是火山岩储层发育的有利区带。总之,根据以上认识,应用地震等资料综合识别预测火山岩总个数为272个,并评价出一类火山岩127个、二类火山岩96个和三类火山岩49个,为下一步勘探部署提供了依据。

The Mesozoic volcanic rocks are the major reservoirs for the deep-buried gas in Songliao Basin. Comprehensive study shows that the formation of high-quality reservoir of Mesozoic volcanic rocks in Songliao Basin is controlled by lithology, lithofacies, fracture and diagenesis. The top of the flood facies, fracture-developed acidic explosive facies are the major development area of high-quality reservoirs. The volcanic lithology which controls the growth of pore is thought as the basis for the formation of high-quality reservoirs. The comparative studies on physical properties of different volcanic lithology indicate the acidic volcanic rocks are preponderant type of reservoir rocks. A whole and independent volcanic edifice is composed of volcanic conduit facies, flood facies, explosive facies, extrusive facies and volcano sedimentary facies from core to edge. A comparative analysis illustrates that the volcanic lithofacies control distribution of high-quality reservoirs in independent volcanic edifice and explosive facies and the top of flood facies around volcanic crater are favorable zone for reservoirs. Deep fractures, which not only betterment filtering conditions of seepage flow, but also impel growth of secondary pores, are important pathways for deep fluids, and key factors for buildup of gas pool with high production. Besides, the high- angle fractures densely developed are easy to form favorable reservoir zones with the assemblage of high-angle fractures and dissolution pores. Based on above conclusion, there are 272 volcanic edifices comprehensively identified in whole basin on the basis of seismic data and so on, with first class of 127, second class of 96 and third class of 49, which provided the basis for exploration deployment.