鄂尔多斯盆地北部十里加汗区带致密砂岩储层流体赋存状态及分布特征

鄂尔多斯盆地北部十里加汗区带上古生界高产气层与低产气层、(含气)水层共存分布,目前对其气水分布的特征、规律及影响因素认识不清,制约了该区天然气勘探开发的进程。为此,统计分析了该区上古生界地层水的矿化度、pH值及离子含量等数据,发现该区地层水水型基本为CaCl_2型;进而利用钻井岩心、录井、测井及分析测试等资料,结合地层水地球化学特征分类评价结果,厘清了地层水的成因、类型、控制因素和空间分布特征,并建立了该区气层、水层和干层的测井识别图版,明确了储层流体的赋存状态与分布规律。结论认为:1 CaCl_2型地层水指示该区地层封闭性好,有利于天然气聚集成藏;2该区储层流体存在自由水、毛细管水和束缚水3种赋存状态,自由水主要分布在区带西部,束缚水主要分布在区带东部,而毛细管水则在全区普遍存在;3将所建立的测井识别图版在该区锦86等井进行了应用,识别结果与试气结果基本一致,表明该识别图版能够有效识别气水层。

Occurrence and distribution characteristics of fluids in tight sandstone reservoirs in the Shilijiahan zone,northern Ordos Basin

High-yield gas layers, low-yield gas layers and (gas bearing) water layers of Upper Paleozoic coexist in the Shilijiahan zone in the northern Ordos Basin, but gas- water distribution characteristics, laws and influence factors are not understood well, so the exploration and development of natural gas in this zone are restricted. In this paper, statistical analysis was carried out on the data of Upper Paleozoic formation water in this zone, e.g. salinity, pH value and ion concentration. It is shown that the formation water in this zone is of CaCl₂ type. Then, the origin, types, controlling factors and spatial distribution characteristics of formation water were figured out by using core, mud logging, well logging and testing data, combined with the classification and evaluation results of geochemical characteristics of formation water. Besides, the logging identification chart of gas, water and dry layers in this zone was established. Finally, the occurrence and distribution laws of reservoir fluids were defined. The formation water of CaCl₂ type indicates a good sealing capacity in this zone, which is favorable for natural gas accumulation. It is indicated that the reservoir fluids in this zone exist in the state of free water, capillary water and irreducible water. Free water is mainly distributed in the west of this zone, irreducible water in the east, and capillary water in the whole zone. The logging identification chart has been applied in many wells in this zone like Well Jin 86. The identification result is basically accordant with the gas testing result. It is verified that gas and water layers can be identified effectively based on this logging identification chart.