渤海海域明下段岩性油藏油柱高度分布规律及影响因素

Distribution law and influencing factors of oil column height in lithologic reservoirs in lower member of Minghuazhen Formation in Bohai Sea

渤海海域明下段岩性油藏特征、储量规模差异大,油柱高度作为油藏评价的关键参数,直接影响油藏储量规模,其分布规律及影响因素认识不清。基于渤海海域约460个明下段岩性油藏勘探开发数据,在充分了解地质背景的基础上,利用统计手段并结合地球化学证据,厘清了浅层明下段岩性油藏油柱高度空间展布规律,通过进一步分析油柱高度与油气充注强度、区域盖层展布、圈闭类型和断砂耦合程度等成藏要素关系,明确了油柱高度影响因素。结果表明:①受油气充注强度控制,明下段岩性油藏油柱高度平面上具有“凸起区小、凹陷区大”特征,平均油柱高度相差约2倍;②受区域盖层控制,纵向上具有“盖层之上油柱高度小、盖层之下油柱高度大”特征,下部Ⅲ/Ⅳ油组平均油柱高度为Ⅰ/Ⅱ油组约2倍;③受油气汇聚部位与侧封保存能力控制,高点依靠断裂侧封油藏油柱高度普遍高于岩性尖灭油藏的油柱高度,平均油柱高度相差约2.5倍;④明下段油气成藏受断砂耦合程度影响,但凸起区与凹陷区断裂油气运移能力差异较大,凸起区切穿馆陶组区域油气输导层断裂可起到运移作用,而凹陷区切穿深部汇聚脊的断裂才可作为有效的油源断裂。渤海海域明下段岩性油藏油柱高度分布规律及影响因素,对后续岩性油藏价值勘探、精细勘探具有借鉴意义。

The characteristics and reserve scale of lithologic reservoirs in the lower member of Minghuazhen Formation in the Bohai Sea are quite different.As a key parameter of reservoir evaluation,the height of oil columns directly affects the reserve scale of reservoirs,but its distribution law and influencing factors are not clear.Based on the exploration and development data of about 460 lithologic reservoirs in the lower member of Minghuazhen Formation of Bohai Sea,the spatial distribution law of oil column height in shallow lithologic reservoirs in the lower member of Minghuazhen Formation was clarified by using statistical means and geochemical evidence on the basis of fully understanding the geological background.By further analyzing the relationship between oil column height and oil and gas charging intensity,regional cap layer distribution,trap type,fault-sand coupling degree,and other reservoir forming elements,the influencing factors of oil column height were clarified.The results show that:①Controlled by oil and gas charging intensity,the oil column height in lithologic reservoirs in the lower member of Minghuazhen Formation has the characteristics of small lifted areas and large depressed areas on the plane,and the average oil column height difference is about two times.②Controlled by the regional cap layer,the oil column height is small above the cap layer but large below the cap layer in the vertical direction.The average oil column height in the lowerⅢ/Ⅳoil group is about two times that in theⅠ/Ⅱoil group.③Controlled by the location of oil and gas accumulation and the preservation ability of side sealing,the height of oil columns in the faulted side sealing reservoir is generally higher than that in the lithologic pinch-out reservoir,and the average oil column height difference is about 2.5 times.④Affected by the fault-sand coupling degree,the migration ability of oil and gas in the faulted uplifted area and the depressed area is quite different.In the uplifted area,the faults that cut through the oil and gas transport layer in the Guantao Formation area can play a migration role,while in the depressed area,only the faults that cut through the deep convergence ridge can serve as effective oil source faults.The distribution law and influencing factors of the oil column height in lithologic reservoirs in the lower member of Minghuazhen Formation in Bohai Sea provide a reference for the subsequent value exploration and fine exploration of lithologic reservoirs.