Yulin Gas Field In Shanxi Sandstone Reservoir And Gas Into The Reservoir Characteristics

Prospecting for natural gas in Upper Paleozoic of Ordos basin has obtained great process in recent years. Four large-scale gas fields, with respective reserves of over 100 billion cubic meters, have been found by taking lithologically subtle gas reservoirs as the main object of exploration. One of these is Yulin gas field which is famous for its good developed reservoirs and stable production. So it has become one of the stable gas sources of "West-East natural gas transporting project".In this paper, the research into the microscopic pore structure and macrcoscopic distribution of the reservoir beds, and factors controlling the gas reservoir forming, has been conducted so as to summarize the law of formation of gas reservoirs of Yulin gas field.The paper adopts a great deal of experiment analysis data such as cast thin section, scanning electron microscopy (SEM), intrusive mercury curve, grain-size analysis, cathodoluminescence microscopy(CLM) and so on. At the same time, well-logging data and related research means are fully applied, combined with outcrops, profiles and core observation. On the basis of sedimentary system division and sedimentary facies study, characteristics of reservoir parameters and its distribution are quantitatively studied, by application of reservoir geological theory. Relatively high permeability sandstone reservoir features and its cause of formation in Snanxi Formation are analyzed from macroscopic and microscopic views. The pattern of gas reservoir formation and law of gas accumulation in Shanxi Formation in Yulin gas field, Ordos basin are studied with combination of synthetical study of distribution of sandstone reservoirs and their capping beds with gas generation and migration. At the same time, the division of reservoir combination and law of distribution of different reservoir combination are studied according to the geological features of Upper Paleozoic reservoirs of Yulin gas field.It is considered that the shallow delta depositional system is mainly developed in Shanxi Formation of Yulin gas field. Their reservoir bodies are large-scagle complex sandstone system. High proportion of quartz content is base of efficient reservoirs. The main pore type is intergranular pores and solution openings. Early hydrocarbon injection is a favorable factor to prevent intergranular pores from destroying. Middle to large grain-size sandstone is the most favorable target of nature gas exploration in this area. The characteristics of Shanxi Formation are inside source reservoir combination development. Coal layers of delta plain-paludal facies, melanocratic mudstone and distributary channel sandbodies cross and overlay. All of formation of a good assemblage spatially is the most important factor to form the Yulin gas field.