论文部分内容阅读
川东北地区在三叠系飞仙关组飞一段—飞二段沉积时期为孤立台地,发育了多个向上变浅的鲕粒滩沉积旋回,且飞二段沉积时期在孤立台地内部形成了膏质泻湖沉积。在孤立台地背景下发育的储层主要岩性为残余鲕粒泥—粉晶白云岩、残余鲕粒粉—细晶白云岩和晶粒白云岩。在向上变浅的鲕粒滩沉积旋回背景下,大气淡水淋滤导致每个向上变浅的旋回自上而下依次为:致密的泥晶白云岩→粒内溶孔(或铸模孔)型残余鲕粒泥—粉晶白云岩→残余粒间溶孔型残余鲕粒粉—细晶白云岩→晶间孔型晶粒白云岩。储层岩石学特征及地球化学分析表明,飞仙关组白云岩储层经历了2期主要的白云石化作用,第一期为渗透回流白云石化作用,第二期为埋藏白云石化作用;渗透回流白云石化增加了岩石强度、抑制压溶和胶结作用,有利于孔隙保存,而埋藏白云石化造成一定的减孔;埋藏溶蚀作用对早期孔隙进行扩溶,增加了储层渗透率,但并不大规模增加储层的整体储集空间。综合分析川东北地区沉积背景、储层岩石学特征、地球化学特征表明,大气淡水淋滤是优质储层形成的先决条件,渗透回流白云石化是优质储层保存的关键因素。
In the northeastern Sichuan area, during the deposition of Feixianguan Formation in the Triassic, the depositional stage of the second member of the Feixianguan Formation was an isolated platform, a number of oolitic beach sedimentary cycles developed upwards were developed. During the deposition of the second member of the Second Member, an ointment was formed in the isolated platform Sedimentary sediments. The main lithology of reservoirs developed in the isolated platform background are residual oolitic dolomite-dolomite, residual oolitic grain-fine crystalline dolomite and crystalline dolomite. In the context of an uplifting oolitic beach sedimentary cycle, atmospheric freshwater leaching resulted in each updip going from top to bottom: dense dolomite → intragranular dissolution (or mold hole) type remnants Oolitic Mud - Powdered Dolomite → Residual Intergranular Soluble Oolong Flour - Fine Grain Dolomite → Intergranular Mesolithic Dolomite. The petrological and geochemical characteristics of the reservoirs show that the dolomite reservoirs of Feixianguan Formation experienced two major stages of dolomitization. The first stage is dolomitization of infiltration and the second stage is burial dolomitization. Dolomitization increases the rock strength and suppresses the pressure-dissolving and cementation, which is favorable for the preservation of pores, while burial dolomitization results in some pore-reduction. Buried dissolution can dissolve early pores and increase reservoir permeability but not large Scale to increase the overall reservoir storage space. The comprehensive analysis of the sedimentary background, reservoir petrology and geochemical characteristics of the northeastern Sichuan Basin shows that the leaching of atmospheric freshwater is a prerequisite for the formation of high-quality reservoirs, and the infiltration reflux dolomitization is the key factor for the preservation of high-quality reservoirs.