鄂尔多斯盆地TH坳陷某地区致密油富集高产主控因素

Main controlling factors of tight oil enrichment and high yield in acertain area of TH depression in Ordos Basin

鄂尔多斯盆地TH坳陷某地区油藏储层致密,具有良好的油气勘探潜力,但致密油富集高产的主控因素不明确,严重制约着该区的高效勘探开发。利用地震、钻井、测井、地球化学和生产动态资料,开展研究区油藏地质特征研究,梳理延长组8段(以下简称长8段)致密油成藏条件,建立其主要成藏模式,识别致密油富集高产的主控因素。研究表明:①延长组7段(以下简称长7段)优质烃源岩及上部泥岩盖层广泛展布,长8段水下分流河道有利储层发育,油气由长7段烃源岩向下充注到长8段砂体中,圈源匹配及保存条件有利,形成了致密砂岩油藏;②储集砂体的规模及物性控制着石油储量及含油气丰度,燕山期构造形成的裂缝改善了致密砂岩物性,对应的裂缝发育区是日产油量大于1 t的主要区域;③水平段钻遇断距较小的正断层上升盘开发效果较好,水平段钻遇断距较大的正断层下降盘开发效果较差,有利储集相带、有效裂缝改造和井位配置关系是控制致密油富集高产的主要因素。研究成果对研究区后续井位部署及油藏开发具有指导意义。

A certain area of TH depression in Ordos Basin has tight reservoir and good oil-gas exploration potential,but the main controlling factors of tight oil enrichment and high yield are not clear,which seriously restricts the efficient exploration and development of this area.The geological characteristics of the reservoir in the study area were studied on the basis of seismic,drilling,geochemistry and dynamic production data.The tight oil accumulation conditions in member 8 of Yanchang Formation(Chang 8 member)were sorted out,and the main accumulation models were established to identify the main controlling factors of tight oil enrichment and high yield.The results are as follows.①The high quality source rock and upper mudstone cover of member 7 of Yanchang Formation(Chang 7 member)are widely distributed,and the underwater distributary channel of Chang 8 member is favorable for reservoir development.The oil-gas is injected downward from source rocks of Chang 7 member to the sand body of Chang 8 member.And the cycle source matching and preservation conditions are favorable,resulting in the formation of a tight sandstone reservoir.②The size and physical properties of the reservoir sand body control the oil reserves and hydrocarbon abundance.The physical properties of tight sandstone are improved by the fractures formed by Yanshanian tectonics,and the corresponding fracture development area is the main area with oil production greater than 1t per day.③The upwelling of normal faults with smaller drilling intervals in the horizontal segment has a good development effect,while the downwelling of normal faults with larger drilling intervals in the horizontal segment has a poor development effect.Favorable reservoir facies belt,effective fracture reconstruction and well location configuration are the main factors controlling tight oil enrichment and high production.The research achievements have guiding significance for the subsequent well location deployment and reservoir development in the study area.