Study On Carbonate Reservoir And Productivity Evaluation In The Tazhong Oil/Gas Field, NW China

Carbonate reservoir development of the earliest are Huabei Oilfield, Sichuan Province, the two parts of the carbonate reservoir spaces are mainly fractured-porous, Tazhong carbonate reservoir main types of reservoir space is vuggy, geological characteristics of the differences led to the development facing different challenges. In the development of carbonate rocks,the use of reserves is a difficult determination, Influence the determination of the size of the development. The determination of the size of sandstone generally taken to the proved reserves multiplied by the oil and gas production rate reached production scale, such as Sichuan, carbonate reservoirs are basically in this way, before the Tarim Oilfield carbonate reservoir development plan preparation process in basically to do so. Carbonate reservoir is now turned over to the proved reserves by homogeneous reservoir model, with the volume method. Before entering the development stage if use the manner of sandstone, with the proven reserves multiplied by oil and gas production rate to determine the size, which is different of the program after the implementation:for in the block of Lungu oilfield use in this way the peak annual output of277,000tons of oil,The actual peak annual output of only168,000tons of oil. In eastern test area of the Tazhong I gasfield proved reserves113.35billion cubic metres,48.65million tons of condensate, such as the methods used sandstone gas multiplied by the gas producing rate of2%(by use of gas reserves in the general rate of2-3%), the area will be built with an annual output of natural gas is about two billion cubic metres, the scale of the experience affirmed by serious too large, the ground construction such as this will cause a huge waste.This paper argues that in determining the scale of the process of development to consider the heterogeneity of carbonate problem, to evaluate the quality of their reserves, in the eastern test area of the Tazhong I gasfield, the programming process using this technology, and production test, combination of seismic data, the use of reserves can be estimated, and then determine the scale of development. Concrete methods are as follows:(1) the use of drilling, logging, testing, test data to classify the wells.Three types:the high-yield wells、 the low-yielding wells、the dry wells;(2) analyze the seismic response characteristics of three types of wells:the high-yield wells has a strong seismic anomaly, the low-yield wells in earthquakes-weak anomaly, the dry wells have small earthquakes abnormal or not abnormal. According to the results of reservoir prediction which partition the reservoir:divided into high-yielding areas, the low-producing and non-reservoir areas;(3) Calculate the high and low-producing oil and gas reservesin the test area:the reserves of the high-yield area was23.73billion cubic metres,oil reserves was21.55million tons; in low areas to14.21billion cubic metres gas reserves, oil reserves of10.45million tons; total geological reserves of natural gas available to37.94billion cubic metres, oil32.01million tons, according to the reserves can be built in the area Natural gas production of about one billion cubic metres.Zoning classification and evaluation of the production capacity. High yield region Lianglitage vertical wells production allocation100,000-150,000cubic metres per day, horizontal wells of the production is twice vertical wells200,000-300,000cubic metres per day; in low-producing areas vertical wells production allocation of25,000cubic metres per day,which based on the production data and the stable time of predication, horizontal wells of the production is three times vertical wells.Tazhong83block based on IPR curve to determine vertical wells and horizontal wells production which are200,000cubic metres per day.According to this idea to solve the Tarim carbonate reservoir evaluation before development issues, effectively guideing the development construction of carbonate reservoir. In eastern test area of the Tazhong I gasfield have been completed and put into production in the end of2010, oil and gas production reached one million tons; Tarim carbonate reservoir with an annual output of crude oil has exceeded one million tons in2010, set foot on the scale of development steps.