鄂尔多斯盆地华庆地区致密油储层异常致密成因分析

Genetic analysis of abnormal tightness of fight oil reservoirs of Huaqing area in Ordos basin

华庆地区长7-长6致密砂岩油储层含油均匀且含油饱和度高，有别于延长组其他地区或层位的低渗、特低渗储层．、以岩心分析资料为基础分析致密油储层的成岩孔隙演化特征，探讨长7-长6储层异常致密成因及目前储层面貌与含油性之间的关系。结果表明，致密油储层异常致密主要由强压实作用引起，另外晚期含铁碳酸盐类胶结作用使储层进一步致密。，导致储层压实作用异常强烈的主要原因是由于砂岩粒度极细，片状矿物云母含量较高，杂基含量高，处于封闭环境以及原油充注的影响导致早期胶结作用较弱，地层压力较低，这些因素大大降低了储集岩的抗压实能力。石油充注时长7-长6低渗、特低渗储层尚未形成，储层并不致密、物性好，储层的古孔隙度至少应当大于19．5％．这是目前致密油储层含油均匀、含油饱和度高的根本原因。

The tight sandstone oil reservoirs of Chang7 to Chang6 in Huaqing area are evenly oil-bearing, high in oil saturation, and different from the lowto extra-low permeability sandstone reservoirs in other regions or horizons of the Yanchang Formation. The diagenetic evolution characteristics of pores in tight oil reservoirs are analyzed on the basis of core analysis data. The genesis of ahnormal tightness of Chang7 to Chang6 reservoirs, and the current relationship between reservoir features and the oil-bearingness are discussed in the paper. The results show that the abnormal tightness of the tight oil reservoirs is mainly caused by the strong compaction. In addition, the ferrated carbonate cementation in the late period made the reservoirs further tight. The main cause of leading to unusually strong compaction of the reservoirs is mainly very fine sand grain size, high content of flaky mineral of mica, high matrix content, and in a closed environment. The impact of crude oil filling leads to early weak cementation and low formation pressure. These factors greatly reduce the anti-compaction capacity of the reservoir rock. When the oil is filling, the lowto extra-low permeability reservoirs of Chang6 to Chang6 have not yet formed. The reservoirs were not tight, with good physical properties. The ancient porosity of the reservoirs should be greater than 19.5%. This is the basic reason for the evenly oil-bearing and high oil-saturated tight oil reservoir at present.