伊犁盆地致密油形成地质条件及资源潜力

Formation geological conditions and its resources potential of tight oil in Yili Basin,China

近年国内外致密油勘探开发和资源评价进展显著。我国致密油主要分布于陆上五大含油气盆地（鄂尔多斯盆地、松辽盆地、准噶尔盆地、四川盆地和渤海湾盆地）,但众多中小盆地的致密油气资源潜力也值得关注。国内外致密油富集区具有＂四大共性形成条件＂,即盆地/凹陷中心宽缓沉积背景、广覆式发育优质烃源岩、大面积分布致密储层、源岩与储层紧密接触,可运用于中小盆地致密油形成条件研究和对比分析。基于野外剖面观测、露头样品和钻井岩心观察、前人资料分析等实物工作量,首次剖析了伊犁盆地致密油形成的地质条件、资源潜力和有利区带。认为伊犁盆地广覆式发育中二叠统（半）深湖相较厚暗色泥岩,生烃指标中等—较好,成熟度和生烃潜力较高。伊宁凹陷大面积分布中二叠统储集砂体,物性差—中等,储层致密。中二叠统源储叠置发育,储盖组合共生,有利于近源聚集,源储基本匹配。伊宁凹陷发育有平缓背景和膏盐层系,保存条件控制着致密油的能否形成和富集。按照致密油资源评价标准和资源起算条件,采用容积法评价伊宁凹陷中二叠统铁木里克组（P2t）致密油地质资源量为3.43×10^8t,技术可采资源量为3 086×10^4t。伊犁盆地具备致密油形成的基本条件,伊宁凹陷南部斜坡带和中央洼陷带有一定的勘探前景,是下一步致密油勘探的主攻方向和有利区带。

The significant progress in tight oil exploration and development and its resource evaluation in domestic and foreign have been made recently.Tight oil in China is mainly distributed in the five maior pet roliferous basins such as Ordos Basin,Songliao Basin,Junggar Basin, Sichuan Basin and Bohai Bay Basin. However,the potential of tight oil resources in many middle-small basins is worthy of attention.There are four common formation conditions in the tight oil enrichment zone at home and abroad, that are wide and slow sedimentary background in basin/depression center, large area distribution of tight reservoir, high quality hydrocarbon source rocks with wide coverage, and reservoirs in close contact with source rocks. Those can be used to study and comparatively analyze the formation conditions of tight oil in medium small basins.Based on the physical workloads such as field profile observation,outcrop samples and drilling core observation and previous data analysis and so on,this paper analyzed the geological conditions, resource po- tential and favorable zones of tight oil formation in Yili Basin for the first time. It is considered that deep- half deep lake facies thick dark mudstones of Middle Permian in Yili Basin widely covered, with medium better hydrocarbon generation indexes, higher maturity and hydrocarbon generation potential.Middle Per- mian reservoir sand bodies distributed with large-area in the Yining Sag, with bad to medium physical property and tight reservoir feature.Middle Permian reservoirs and source rocks are vertically overlapped, with combination of reservoirs and caps. So it is conducive to hydrocarbon accumulation near the source rocks, and the source rocks have basic matching with reservoirs.Flat sedimentary background and gypsum/ salt bed developed in Yining Sag.The formation and enrichment of tight oil can be controlled by the preser vation conditions.According to the evaluation criteria and the initial conditions of tight oil resources,by u sing the volumetric evaluation method,tight oil geological resources of Middle Permian Tiemulike Forma- tion （P2t） in Yining Sag are 3.43 ×10^8 tons, technology recoverable resources of 3086 ×10^4 tons.According to comprehensive evaluation, basic conditions of tight oil forming and certain exploration prospects are pos- sessed in Yili Basin.Related flat sedimentary background and pre-salt strata developed in the central sub- sag belt and southern slope belt of Yining Sag.They should be the main direction of tight oil exploration in the next step and favorable exploration areas.