鄂尔多斯盆地西部奥陶系克里摩里组有效储层发育控制因素

近年来，鄂尔多斯盆地西部奥陶系的天然气勘探取得了一定进展，其中以奥陶系克里摩里组天然气聚集程度最高，但其有效储层发育控制因素复杂，导致勘探效果不理想。基于岩心观察、薄片鉴定、钻录井等资料，系统研究了克里摩里组有效储层发育类型及控制因素，建立了有效储层发育模式。鄂尔多斯盆地西部克里摩里组有效储层类型主要有白云岩晶间(溶)孔、灰岩岩溶缝洞和构造微裂缝，局部发育台缘滩颗粒孔型储层；有效储层发育主要受控于沉积相带、成岩作用、古岩溶风化作用及构造运动，其中潮坪相及台缘滩相为克里摩里组提供了原始储层的物质基础，并在此基础上形成了成岩早期的白云岩晶间(溶)孔和台缘滩颗粒孔型储层；埋藏成岩作用阶段，重结晶作用对原始白云岩储层改造明显，晶体骨架更加稳固，新的晶间(溶)孔形成或经历二次重结晶改造，同时台缘滩颗粒孔的原始结构部分被破坏、充填或改善，形成现今的台缘滩残余颗粒孔；古岩溶风化作用控制克里摩里组中上部岩溶缝洞型储层的发育，高产井主要发育在岩溶斜坡沟槽地带的上槽方向及岩溶高地；多期构造运动不断改造、控制微裂缝系统的发育，形成断裂带周边分布的多孔介质储集体。因此，寻找克里摩里组潮坪相和台缘滩相有利相带、岩溶古地貌上倾部位或断裂带高部位，是下一步勘探的有利方向。

Controlling factors for effective reservoir development of Ordovician Kelimoli Formation in western Ordos Basin

In recent years, some progress has been made in the exploration of Ordovician natural gas in the western Ordos Basin, among which, the Ordovician Kelimoli Formation has the highest degree of natural gas accumulation. However, the controlling factors for effective reservoir development are complicated, leading to unsatisfactory exploration effect. Based on the data of core observation, thin section identification, drilling and logging, the development types and controlling factors of effective reservoir in the Kelimoli Formation were systematically studied, and a development model of effective reservoir was established. The results show that the effective reservoir types of Kelimoli Formation in the western Ordos Basin mainly include dolomite intercrystal (dissolved) pore, limestone karst fracture and structural micro-fracture, and marginal platform granular pore type reservoir is locally developed. The development of effective reservoir was mainly controlled by sedimentary facies, diagenesis, paleokarst weathering and tectonic movement. The tidal flat facies and marginal platform facies provided the material basis for the original reservoir of the Kelimoli Formation, and on this basis, the dolomite intercrystal (dissolved) pore and marginal platform granular pore reservoirs were formed in the early diagenesis. In the stage of burial diagenesis, recrystallization obviously reformed the original dolomite reservoir, and the crystal framework became more stable. New intercrystal (dissolved) pores were formed or underwent secondary recrystallization. At the same time, the original structure of marginal platform granular pores was damaged, filled or improved, and the present marginal platform residual granular pores were formed. Paleo-karst weathering controlled the development of fracture-vuggy reservoirs in the middle and upper parts of the Kelimoli Formation, and high-yield wells were mainly drilled in the upper groove direction of the karst slope groove zone and karst highlands. The multi-stage tectonic movement continuously transformed and controlled the development of micro-fracture system, forming porous media reservoirs distributed around the fault zone. Therefore, it is a favorable direction for further exploration to find favorable facies belts of tidal flat facies and marginal platform facies, updip positions of karst paleo-geomorphology or high positions of fault zone.