注水开发油藏高含水期大孔道发育特征及控制因素——以胡状集油田胡12断块油藏为例

东濮凹陷胡状集油田胡12断块沙三段中亚段（Es3^中）油藏为扇三角洲沉积，其中4至8油层组由于长期注水形成了许多大孔道。综合分析研究区具有明显大孔道的井段所处的沉积微相、砂层厚度和储集层物性，结果表明，宏观上，大孔道主要分布于厚度大干3m的水下分流河道及河口坝微相中；微观上，孔隙度大干20％、渗透率大干100mD的水下分流河道正韵律砂岩中、下部及河口坝反韵律砂岩顶部的中一粗粒砂岩易于形成大孔道。岩石成分成熟度高、成岩演化程度低、长期大规模注水是形成大孔道的主要原因。大孔道形成后，储集层孔隙度增大3％～5％，渗透率增大5～20倍，主要表现为孔喉半径增大；自然电位基线偏移，微电极幅度差和声波时差增大，电阻率降低；相对吸水量明显高于邻层，注水量增大的同时，产液量也增加，但油量下降，注入压力减小。图6表1参19

The middle Shahejie Formation of Block Hu 12, Dongpu Sag belongs to fan-delta deposition. High capacity channels are formed in the 4th 8th sand units due to long time water-flooding developments. They are mainly distributed in the sand beds of subaqeous

The middle Shahejie Formation of Block Hu 12, Dongpu Sag belongs to fan-delta deposition. High capacity channels are formed in the 4^th-8^th sand units due to long time water-flooding developments. They are mainly distributed in the sand beds of subaqeous channel and mouth bar micro-facies whose thicknesses are more than 3 meters, on the lower part of normal grain rhythm of subaqeous channel sandstones and on the top part of reverse grain rhythm of mouth bar sandstones, whose porosity and permeability are over 20% and 100rnD respectively. Their formation is attributed to high maturity, low diagenesis evolution, and long-term water-flooding. The porosity of sandstones increases by 3%-5 % and permeability by 5-20 times, the width of pore throats is enlarged. The base line of spontaneous potential is uplifted, the differences of microelectrode and acoustic travel time increased, resistivity decreased. The water absorption is higher than that in the adjacent beds. As water injection increases, liquid production increases, but oil production and injection pressure decrease.