姬塬油田麻黄山地区长4+5和长6储集层敏感性差异评价

为避免储集层敏感性伤害,提高油田采收率,进行姬塬油田麻黄山地区长4+5和长6储集层的敏感性差异研究。在对研究区岩石学特征、物性特征和孔喉结构特征研究的基础上,用岩心开展敏感性实验,对研究区长4+5和长6储集层的敏感性进行评价,并分析造成长4+5和长6储集层敏感性差异的原因。结果表明,姬塬油田麻黄山地区长4+5和长6储集层以岩屑长石砂岩为主;长4+5和长6储集层的平均孔隙度分别为10.6%和9.4%,平均渗透率分别为0.65 mD和0.25 mD,平均面孔率分别为6.84%和3.67%;研究区长4+5和长6储集层总体上均具有弱速敏、弱水敏、弱盐敏、强酸敏和强碱敏的特点;由于长4+5储集层长石和石英含量较高,高岭石含量较低,其碱敏性和水敏性较长6储集层强;长6储集层则因为黏土矿物含量较高,其盐敏性和酸敏性较长4+5储集层强。在后续的储集层改造中,应严格控制注入地层流体的pH值。

Evaluation on Sensitivity Difference Between Chang 4+5 and Chang 6 Reservoirs in Mahuangshan Area of Jiyuan Oilfield

In order to avoid sensitivity damage and improve oil recovery, the sensitivity difference between Chang 4+5 and Chang 6 reservoirs in Mahuangshan area of Jiyuan oilfield was studied. Based on the analysis of petrology, physical properties and pore-throat structures of the reservoirs in the study area, sensitivity experiments were carried out with cores, then the sensitivities of Chang 4+5 and Chang 6 reservoirs in the study area were evaluated, and the causes for the sensitivity differences between Chang 4+5 and Chang 6 reservoirs were analyzed. The results show that the Chang 4+5 and Chang 6 reservoirs are dominated by lithic feldspar sandstone, and have the average porosity of 10.6% and 9.4%, the average permeability of 0.65 mD and 0.25 mD, and the average surface porosity of 6.84% and 3.67%, respectively. The Chang 4+5 and Chang 6 reservoirs are generally characterized by weak velocity sensitivity, weak water sensitivity, weak slat sensitivity, strong acid sensitivity and strong alkali sensitivity. The Chang 4+5 reservoir exhibits stronger alkali sensitivity and water sensitivity than the Chang 6 reservoir, for its high content of feldspar and quartz and low content of kaolinite, while the Chang 6 reservoir has stronger salt sensitivity and acid sensitivity than the Chang 4+5 reservoir, for its high content of clay minerals. In the subsequent reservoir stimulation, the pH value of the injected fluid to formation should be strictly controlled.