塔里木盆地库车坳陷克深区块深层致密砂岩气藏气水分布特征与成因机理

Gas-water distribution characteristics and formation mechanics in deep tight sandstone gas reservoirs of Keshen block,Kuqa Depression,Tarim Basin

库车坳陷克深区块白垩系巴什基奇克组发育(超)深层裂缝性致密砂岩气藏,为高温高压系统,气水分布关系复杂,给勘探开发带来了挑战。通过系统剖析致密砂岩储层特征、气藏源储关系、气水分布特征等,结合相渗等实验,研究气藏的气水分布成因机制与模式。研究表明,巴什基奇克组致密砂岩基质储集空间以残余粒间孔、粒间溶蚀扩大孔为主,孔喉结构复杂,断层、裂缝形成不同尺度的裂缝网络系统,储层非均质性强;"源储显著分离"是克深区块有别于国内外其他典型"源储互层型或紧邻共生型"致密砂岩气藏主要特征;"源储分离"使得天然气需要通过断层、裂缝系统,经过较长距离的二次运移进入致密储层;天然气充注程度受断层—裂缝系统、裂缝网密度、岩石基质物性与孔隙结构影响,距离裂缝面越近,岩石基质中天然气充注强度越大;在膏盐岩直接盖层影响下,气藏地层水主要通过断层和裂缝网络反排,排替作用是天然气主要的成藏机制;进而将克深地区深层裂缝性致密砂岩气藏气水分布模式归纳为3类,缝网发育的正常气水分布模式、缝网不发育的气水分布模式和局部缝网发育的气水共存分布模式。

The deep fractured tight sandstone gas reservoir of K1bs in Keshen block of Kuqa Depression has a high temperature and high pressure system and very complex gas-water distribution characteristics which takes a great challenge for exploration and production. This article carried out a research on the geneticmechanism and model of gas-water distribution in these gas reservoirs through systematical analyses of reservoir characteristics, source-reservoir relationship and gas-water distribution of tight sandstone gas res- ervoir combined with relative permeability test. Research shows that the tight sandstone reservoir in Klbs has strong reservoir heterogeneity which is demonstrated by matrix with complex pore structure whose pore space gives first place to residual intergranular pore and intergranular dissolution enlarged pore and different scales of fracture network system formed with faults and fractures;Keshen block is distinguished from other domestic and abroad tight sandstone gas reservoirs with adjacent source-reservoir type by re- markable separation of source and reservoir that makes gas a long secondary migration to tight reservoir through faults and fracture systemGas charging level is in control of fault-facture system, fracture densi- ty, matrix physical property and pore structure so that the closer to fracture, the greater reservoir gas char- ging level will be; Under the effect of gypsum-salt cap rocks, gas reservoir water is reverse discharged mainly through faults and fracture network and replacement effect is the main reservoir-forming mecha- nism for gas;and then the gas-water distribution pattern of the deep fractured tight sandstone gas reser- voirs in Keshen block was classified into three types,i.e., normal gas-water distribution pattern with frac- ture network developed, gas-water distribution pattern with fracture network non-developed and gas-water coexistence distribution with fracture network partly developed.