塔河油田奥陶系古径流岩溶带垮塌充填特征

岩溶缝洞是塔河油田主要储集空间，但是它们70％以上的空间被地下河沉积砂泥和洞穴垮塌角砾等物质所充填，其中垮塌角砾约占30％。研究这些垮塌角砾的形成和分布对于岩溶储层地质学具有重要意义。通过野外考察、岩心观察以及测井和地震资料分析，发现径流岩溶带垮塌角砾大小、形态不一，而且与地下河砂泥沉积呈互层出现，颗粒较小的垮塌角砾有被搬运迹象；洞穴规模越大（如厅堂洞和干流洞）、越靠近活动性断层的溶洞和表层岩溶带的溶洞，垮塌角砾岩堆积厚度越大；颗粒较小的（＜2 cm）垮塌角砾岩孔渗性差，颗粒较大者可具有较好的储集性能和含油性，后者构成了塔河油田岩溶缝洞储层的一部分。

Characteristics of collapse breccias filling in caves of runoff zone in the Ordovician karst in Tahe oilfield,Tarim Basin

Fractures and vugs are the major reservoir spaces in Tahe oilfield,but more than 70% of their spaces were filled by underground river sediments and cavern-roof collapse breccias,of which the latter accounts for over 30% in the cavern fillings.It is of great significant for reservoir geology of karst carbonates to study the formation and distribution of the collapse breccias.Combined with investigations on the Ordovician karst outcrops,observations of core samples and interpretations on well logging and seismic data,it was found that the collapse breccias are various in sizes and shapes in which small size of the breccias are transported by underground river and interbedded with sedimentary debris layers in caverns.The larger the caverns were(such as chamber caverns and main channel caverns)and the closer to active faults and epi-karst zone,the larger the thickness of the collapse breccias are.Porosities and permeabilities of the collapse breccias are low when the grain size of the breccias is smaller than 2cm.The breccias with bigger grain size would have better reservoir physical property and oil-bearing property,and thus should be one part of reservoir rocks in Tahe oilfield.