STUDY OF THE CHARACTERISTICS OF CARBONATE RESERVOIRS IN LUNNAN AND TAHE OIL FIELDS, THE TARIM BASIN—TAKING WELLS S107 AND LG40 AS EXAMPLES

Tahe and Lunnan oil fields are respectively located in the south and the north of the Akekule Uplift,the Tarim Basin.In terms of structural location,it was characterized by structural high in the north and low in the south.The difference of structural actions and the late alteration resulted in the different characteristics of the reservoirs in the two parts.According to the comparative study of the reservoir characteristics in the Well S107 and the Well LG40,some new findings have been got.The Well LG40 is located at the Lunnan oil field which was in the structural high in the north of the Akekule Uplift.The Ordovician carbonate reservoirs are relatively thin thickness.Most part of the Ordovician sequence is absent,with the only stratum is the Yingshan group of the Middle—Lower Ordovician.However,owing to its near the upper unconformity surface,the weathering crust reservoirs was developed and the fractures and the cores were well developed to form an excellent reservoirs.The Tahe oil field where the Well S107 located at is in the southern slope area of the Akekule.The Ordovician sediments were comparatively integrity.But the quite thick Upper Ordovician un-karstic strata made the Middle—Lower Ordovician obstructed from the karst alteration.Besides,due to the Middle—Lower Ordovician sequence was far from the upper unconformity surface,the development of the cores,fractures and holes were limited.The reservoir quality is much poorer compared with the reservoir of the northern area in which the Upper Ordovician was absent.