二连盆地阿南低渗透火山碎屑砂岩油藏储层特征及其对开发的影响

Reservoir characteristics of low-permeability pyroclastic sandstones and their influences on petroleum development in A'nan oilfield of Erlian Basin

梁官忠 姜振学 刘忠 尹志军 申保华 马俊恒

Liang Guanzhong Jiang Zhenxue Liu Zhong Yin Zhijun Shen Baohua Ma Junheng

阿南砂岩油藏储集岩以长石岩屑砂岩为主,属近源快速沉积的水下扇砂体,且沉积时受火山活动影响明显。岩石中火山成因岩屑及凝灰质胶结物含量高,岩石成分成熟度和结构成熟度均较低,储集体具有埋藏浅但压实作用、胶结作用等成岩后生作用强烈的特点,导致油层原生孔隙不发育,主要发育次生溶孔。孔喉以微喉为主,吼道分选差、储渗能力较弱,油藏具有典型的低渗火山碎屑砂岩油藏特征。油藏注水开发后,由于水敏和速敏等因素的影响,孔隙结构进一步变差,油层驱替压力上升,无水采收率和最终驱油效率下降,油藏注水开发表现出注水压力不断上升、地层憋压现象明显但油井供液能力普遍不足等特征。随后开展了细分开发层系和加密井网等措施,开发状况得到一定程度的改善。

The reservoir rocks of A'nan sandstone oilfield are dominated by feldspar lithic sandstone,and are proximal subaqueous fan deposits with prominent influences of volcanic activity.They feature in high content of pyroclastic debris and tufaceous cements,low composition maturity and structure maturity.Although their burial depth is shallow,epidiagenesis such as compaction and cementation are intense,leading to the poor development of primary porosity.As the major secondary pores,the dissolution pores feature in micro-pore throat and poor sorting of pore throat,resulting in poor storage capacity and permeability.Therefore,A'nan oil reservoir is typical low permeable pyroclastic sandstone reservoir.The pore structure deteriorates during water flooding due to various factors such as water sensitivity and velocity sensitivity.As a result,the displacement-pressure increases,while water-free oil recovery and ultimate oil displacement efficiency decrease.During waterflooding,water injection pressure increases continuously,and pressure buildup is significant,but well deliverability is commonly low.Several measures such as layer-subdivision and infill drilling are carried out to improve oilfield development.

10.11743/ogg20130107