惠州凹陷西南部文昌组储层特征及优质储层主控因素

Reservoir Characteristics and Main Controlling Factors of High-quality Reservoirs in Wenchang Formation in Southwestern Huizhou Sag

珠江口盆地惠州凹陷西南部文昌组碎屑岩储层埋深普遍大于3300m,多数为特低-低孔渗储层,且非均质性强,寻找优质储层是进行深层勘探的重要前提。利用惠西南地区文昌组5口井的钻井、测录井及分析化验资料,分析储层岩石学特征、物性特征、孔隙类型等微观特征,结合构造-沉积背景,研究优质储层发育的主控因素。研究结果表明,惠州凹陷西南部文昌组下段岩石类型主要为长石岩屑砂岩和岩屑砂岩,为特低-低孔隙度、超低-低渗透率储层,储层孔隙主要由粒间孔、粒内溶孔及晶间微孔构成。储层质量主要受沉积作用和成岩作用共同控制,压实和胶结作用主要对储层起破坏作用,后期有机酸溶蚀长石,形成次生孔隙,明显提高了孔隙度。在3400~3500m深度段,发育一套以粒间孔为主的中孔渗优质储层,孔隙度可达20%,渗透率可达411mD。强水动力改造的沉积背景、早期绿泥石包壳保护、烃类早期充注的共同作用,是深部优质储层形成的主要原因。

The clastic reservoirs of Wenchang Formation in the southwestern Huizhou Sag in the Pearl River Mouth Basin are generally buried deeper than 3300m,and most of them are of ultra low-low porosity and permeability and strong heterogeneity.Finding high-quality reservoirs is an important prerequisite for deep ex-ploration.Based on the drilling,logging and analysis data of five wells in the Wenchang Formation in the southwestern Huizhou area,the petrological characteristics,physical properties,pore types and other microscopic characteristics of the reservoirs are analyzed,and main controlling factors of the development of high-quality reservoirs are studied in combination with the structural-sedimentary background.The research results show that the Low Member of Wenchang Formation in the southwestern Huizhou Sag is dominated by feldspar lithic sandstones and lithic sandstones,which are ultra low-low porosity and ultra low-low permeability reservoirs,and the reservoir pores are mainly composed of intergranular pore,intragranular dissolved pore and intergranular micropores.The quality of reservoirs is mainly controlled by sedimentation and diagenesis.The com-paction and cementation mainly destroy the reservoirs.In the later stage,the organic acid dissolves the feldspar to form secondary pores and then the porosity may be significantly increased.In the depth of 3400-3500m,a set of high-quality reservoir with the medium-porosity and permeability dominated by intergranular pores are developed with the porosity of 20% and the permeability of 411mD.The combined action of the sedimentary background under the strong hydrodynamic stimulation,the protection of early chlorite coatings,early hydrocarbon charging are the main reasons for the formation of deep high-quality reservoirs.