塔河地区奥陶系一间房组微裂隙颗粒灰岩储集体的发现与勘探意义

DISCOVERY AND EXPLORATION SIGNIFICANCE OF MICROFISSURE GRAIN LIMESTONE RESERVOIRS IN THE ORDOVICIAN YIJIANFANG FORMATION OF TAHE AREA

塔河地区位于塔里木盆地沙雅隆起南部,在奥陶系大型古潜山背景上形成了塔河地区奥陶系大型地层不整合-古岩溶圈闭。该圈闭的进一步勘探表明,圈闭主体部位储集层为奥陶系下统鹰山组岩溶缝洞型储集体,而圈闭南部新发现奥陶系下统一间房组颗粒灰岩孔隙型储层。该类储层主要储集空间为粒间孔和针尖状溶蚀孔,在微裂缝、缝合线等连通下形成了厚度约20～30m、分布约200km2的较广泛的层状孔隙型储层。成像测井资料的进一步解释处理发现,其溶孔孔隙度达5%。该类储层主要受台地边缘生屑滩相展布的控制,后期溶蚀作用有利于改善其储集性能。颗粒灰岩储集体与上覆奥陶系中—上统泥质灰岩、石炭系下统泥岩区域性盖层组成良好的储盖组合,并具有良好的封闭性,在烃源区高成熟油气多期充注下形成了中质—轻质油藏,具有良好的勘探效益。在已完钻的几口探井中经酸压获高产油流,充分展现了这一勘探领域的巨大潜力。

Tahe area is located in the southern part of the Shaya Uplift, the Tarim Basin. A largescale stratigraphic unconformablepaleokarst trap was formed on the background of the largescale Ordovician fossil buried hill. The further exploration of the trap showed that reservoirs in the main part of the trap were the karst fissuretyped reservoirs of the Lower Ordovician Yingshan Formation, and the grain limestone poretyped reservoirs of the Lower Ordovician Yijianfang Formation were newly discovered in the southern part of the trap. The storage space of this type of reservoirs was dominated by intergranular openings ang pinpointlike solution openings, which were connected by microfissures and sutures to form 2030m thick and 200 km2 spread more wideranging layered poretyped reservoivs. The further interpretation and treatment of imaging logging data revealed that the porosity of solution openings was about 5%. This type of reservoirs were mainly controlled by the distribution of tableland marginal bioclastbank facies, and paulopost solution was advantageous to the improvement of their storage performance. The grain limestone reservoirs and the upperlying regional caprocks of the MiddleUpper Ordovician argillaceous limestone and the Lower Carboniferous mudstone constituted a good reservoircaprock assemblage with good sealing performance. Under the multiple periods of highmature hydrocarbon injection by hydrocarbon source areas,mediumlight oil pools with good exploration benefits were formed. In some prospect wells completed, highproductive oil flow was obtained through acid fracturing treatment. This expressed tremendous potential of the exploration field.