胜利探区低渗透油层产液量不足的原因及改造对策

Causes and countermeasures for low liquid production in low-permeability reservoirs in Shengli region

近年来,在胜利探区深层相继发现了累计数亿吨的低渗透控制和预测储量,这些储量多来源于致密砂岩和强胶结碳酸盐岩储集层。由于单井产液量低,一直未能有效实现探明储量的升级。为分析原因,提高产能,利用了部分低渗低产井的含油岩心资料和实验检测数据,将产液量不足的原因与油层复杂的岩性特征、原油性质和工艺配套措施相联系加以分析,确定了低渗透储层产液量不足的内、外因素,即岩石致密结构导致的低溢出量、岩石非均质性导致的油水关系不落实、黏土多样性导致的多敏性并存、含油饱和度不足导致的不饱和间溢以及油藏内油质偏稠导致的流动性偏差等,是油层产液量不足的"内因";压裂实施过程中液相冲击力造成的储集空间内黏土微粒堆挤和酸化过程中酸液与储层性质不配伍形成的副产物(多为沉淀物),使储层渗透性进一步降低,是油层产液量不足的"外因"。针对不同的问题和诱发原理,对部分单井层分别制定了增产改造措施,实施后取得了明显增油效果。

Majordiscoveries have been made in the tight sandstone and strongly-cemented carbonate reservoirs in the deep formations of the Shengli region in the recent years. However, provenreserves have failed to increasesince the productionratefor liquids is low in a singe well. Oil-bearing core samples were collected from the wells with low permeability and low productionrate, and were tested to find out the causes for that low liquid productionrate. The complicated lithologic characteristics of reservoirs, crude oil properties and technical supporting measures were correlated with liquid shortage. Some internal and external factors for low liquid productionrate were identified. Low flow amountsresultingfrom the tight rock structure, an unclear oil/water relationship resultingfrom rock heterogeneity, various sensitivityresultingfrom clay variety, discontinuous output of crude oil resulting from low oil saturation, and oil flow deviationresultingfrom heavy oil were regarded as the internal causes. Clay particles in pore throats during fracturing and deposits from the reaction between acid frac-fluid and the reservoir made permeability become worse, which were regarded as the external causes. For different problems, the improvement measures for some single well layerswere formulated and producedgood results.