Method for predicting primary capacity of compact carbonate rock gas bearing formations

Abstract

The invention relates to a method for quantitatively predicting primary capacity of compact carbonate rock gas bearing formations. The method includes building a logging explanation database of a carbonate rock gas bearing formation region, and making an Ig-Qg capacity predicting plate by the aid of data of the database according to the characteristic that gas containing indexes Ig of gas bearing formations which have the same types in an identical region or similar reservoir features and are confirmed by gas testing is linearly relevant to primary stable capacity Qg of the gas bearing formations on a scatter diagram; building a capacity predicting equation of Qg=AXIg+B; utilizing the data of the database to regionally draw the Ig-Qg capacity predicting plate, building the capacity predicting equation of Qg=AXIg+B to predict the primary stable capacity of the carbonate rock gas bearing formation region, comparing an output predicted result with an actual measured result, and inputting the predicted result into the logging explanation database if a relative error is smaller than 20%; and repeating the above steps if the relative error is larger than 20% until the relative error is smaller than 20%, and then inputting a result into the logging explanation database. The method is applied to more than 150 wells and formations in a Sichuan basin, an absolute value of a capacity predicting relative error is smaller than 20%, key parameters of capacity prediction are calculated simply and conveniently, and field practicality is high.

Description

technical field [0001] The invention relates to geological and natural gas exploration and development, and is mainly used for predicting the initial production capacity of tight carbonate rock gas layers in the process of drilling and logging, and providing key parameters for reservoir evaluation. It belongs to the fields of geology, well logging and mud logging services, especially the interpretation and evaluation of mud logging data. Background technique [0002] During the drilling of carbonate rock natural gas wells, the drill pipe open-hole testing technology or the "perforation-testing" joint technology after well completion is usually used to test the gas layer for production, and then evaluate the productivity of the gas layer. [0003] For tight carbonate gas layers, it is difficult to directly obtain gas layer productivity parameters using drill pipe open-hole testing technology. In the open-hole well test, due to the high risk of acidizing construction, the "ac...

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Problems solved by technology

After the "perforation-acid fracturing-test (triple operation)" after the completion of the well, it is no longer possible to continue drilling, which affects subsequent drilling and the discovery of gas layers in the lower formations

[0004] At present, there is no practical method for predicting the initial stable productivity of tight carbonate gas reservoirs using mud logging data.

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