Formation and Controlling Factors of Effective Weathered Crust Carbonate Reservoirs——Taking the Yingmaili-Yaha Area of Tarim Basin as an Example

In recent years,the marine oil and gas exploration in China has made great progress and lots of high quality carbonate reservoirs in deep strata have been found.As one of the most important carbonate reservoirs,the weathered crust reservoir has taken much more attention.Especially in the Tabei area of Tarim Basin,plenty of hydrocarbon resources are stored in the weathered crust reservoir,which arouses lots of concerns at present.In the Yingmaili-Yaha area of Tabei,the main accumulation spaces of the Cambrian-Ordovician weathered crust are dissolved pores,fractures and caverns,and these reservoirs have good physical properties,great thickness and large distribution range.Research shows that the formation of the reservoir in this area is restricted by factors such as early stage sedimentary facies,weathering and leaching,fractures created by the tectonic movement and associated denudation.The Weathering crust karstification and the tectonic disruption has greatly improved the nature of the accommodation spaces,as a result,in the Yingmaili-Yaha area,even buried in the depth of about 6 000m,high porosity and permeability weathering crust reservoirs are still well preserved.There are many controlling factors,such as paleogeomorphology,tectonic subsidence and uplifting,weathering and leaching time,paleoclimate,etc,thus forming lots of dissolved pores,fractures and caverns,and they are mainly distributed in the depth of 150m under the weathering front,and it is up to 200m in local areas.