塔中地区西部奥陶系岩溶发育特征及其与关键不整合面的关系

THE DEVELOPMENT CHARACTERISTICS OF ORDOVICIAN KARSTS AND ITS RELATIONSHIP TO KEY UNCONFORMITIES IN THE WESTERN PART OF THE MIDDLE TARIM BASIN

近年来,在研究区内新钻探了4口新井,塔中地区首次在构造带末端的奥陶系中获得了较好的油气显示,展示了该区良好的油气勘探前景。碳酸盐岩储层以缝洞为主要储集空间,因此,深入分析溶蚀孔洞发育特征,探索其分布规律,对于有利储集区带的预测至关重要。本次研究中首次利用FMI成像测井资料对该区溶蚀孔洞发育情况进行了精细的识别,从而有效的确定了溶蚀孔洞的发育形态、大小、疏密程度及其纵向发育规律。明确了该区溶蚀孔洞主要发育在下奥陶统鹰山组中,且具有在鹰山组顶部岩溶带发育稳定,在鹰山组内部埋藏岩溶带发育弥散的特点。在此基础上,初步探讨了奥陶系两个关键不整合面(T70和T74)对岩溶发育的不同影响,探索碳酸盐岩岩溶型储层研究的新思路。

The data from the 4 newly drilling wells manifest that there are good oil and gas shows in Ordovician reservoirs at the end part of the tectonic belt, Middle Tarim Basin, and that the studied area is a potential exploration belt. Because the reservoir styles in Ordovician carbonates are main karsts, it is very important for predicting favorable reservoir belts to deeply discussed the development and distribution characteristics of carsts. In this paper, with the first application of FMI the development conditions of the solution holes in the studied area have been exquisitely identificated, and its development shape, size, density, and longitudinal trend all have been efficiently confirmed. The results obtained manifest that the solution holes in this area are mostly developed in the Yingshan Formation, Lower Ordovician, that the karst belt is stable at the top of the Yingshan group and is dispersed within the deeper Yingshan Formation. Furthermore, as a new study ideas on carbonate karst reservoir, the contribution of the two key unconformity（T7^4 and T7^0） to the karst development rule is briefly discussed on the basis of former researches.