鄂尔多斯盆地双龙地区延长组长6致密油成藏主控因素

双龙地区为延长油田长6致密油勘探的重要区域,目前对区块致密油富集主控因素的认识仍存不足。基于此依据19口井的岩心资料、128口井的测井资料及26口井的试油试采资料,结合19口井的实验测试结果在成藏地质条件和致密油聚集特征进行精细分析的基础上对致密油成藏主控因素进行研究。结果表明:研究区致密油成藏地质条件良好,油水分布复杂。沉积微相及储层物性为控制致密油成藏的首要条件,单层为4 m以上的浊积水道砂体,储层孔隙度大于5.4%,渗透率大于0.16×10^-3μm²,致密油易富集;过剩压力影响油藏的平面分布,致密油多聚集在过剩压力系数相对低值区(过剩压力系数约为0.24~0.32);泥岩盖层能够形成良好的遮挡,有利于致密油就近聚集,也是造成油水关系复杂的重要原因。因此在满足砂体发育、储层物性条件的前提下,遵循过剩压力系数局部低值、泥岩盖层有效遮挡的原则,划定长6段有利勘探区域11个,以指导双龙地区致密油勘探开发工作。

THE MAIN CONTROLLING FACTORS OF TIGHT OIL RESERVOIR FORMA-TION OF THE CHANG6 MEMBER OF TRIASSIC YANCHANG FORMATION IN SHUANGLONG AREA,ORDOS BASIN

Shuanglong Area is an important exploration target for Chang 6 tight oil in Yanchang Oilfield.However,the main controlling factors of tight oil enrichment in the block cannot be well understood yet.Based on the core data of 19 Wells,logging data of 128 Wells and oil test and production data of 26 Wells,combined with the experimental test results of 19 Wells,the main controlling factors of tight oil accumulation in the Shuanglong area are studied through fine analysis of reservoir forming geological conditions and tight oil accumulation characteristics.The results show that the Shuanglong area possessed good geological conditions for tight oil accumulation with complex distribution of oil and water.Sedimentary microfacies and reservoir physical properties are the primary conditions to control the accumulation of tight oil.Single layer of turbidite channel sand body over 4 m thick,with reservoir porosity over 5.4%and with permeability over 0.16×10^-3μm²,makes the tight oil easy to be concentrated.The overpressure affects the horizontal distribution of the reservoir,and the tight oil is mostly concentrated in the area with relatively low overpressure coefficient(about 0.24-0.32).The mudstone cap can form a good shield,which is conducive to the nearby accumulation of tight oil,and is also an important reason for the complication of oil-water relation.Therefore,under the precondition of satisfying the development of sand body and reservoir physical properties,as well as following the principle of local low value of overpressure coefficient and effective shielding of mudstone cap rock,11 favorable exploration areas of Chang 6 Member have been delimited to guide the exploration and development of tight oil in Shuanglong Area.