Abstract
For a better guidance of production, a combination of drill stem testing (DST), regional statistical method and pseudo steady-state seepage theory model was used to analyze the productivity of N gas reservoir in light of the complex geological features of the low-permeability thick-layer. Firstly, the DST method was used to test the N gas reservoir. And then the binomial pseudo-pressure method, binomial pressure square method and exponential method were used to interpret the test data of DST of this formation. Finally, the binomial pseudo-pressure interpretation method was used and the results showed that only the productivity of H3b layer was successfully tested of the four. The H3a, H4b and H5a layers are ultra-low pore and permeability gas reservoirs and the productivity of these layers can’t be explained by the available data due to the short testing time and a non-stationary state of testing pressure and quantity, resulting in the failure of the test. The productivity of the main layers were estimated and forecasted by the regional statistical method and the theoretical model of pseudo steady-state seepage, taking the arithmetic average value of the regional statistical method and the theoretical formula as the final value of absolute open flow rates(AOF). The final calculation results are as follows: the AOF of main gas layers H3a, H3b, H4b and H5a in N gas field is 31.30×104m3/d, 388.92×104m3/d, 20.82×104m3/d and 30.80×104m3/d, respectively. This method may sheds light on verifying and calculating the productivity of gas wells and determining the reasonable production allocation of gas wells.
Highlights
The low-permeability gas reservoirs in China are rich in resources and have great development potential
drill stem testing (DST) is a work aiming at obtaining the parameters of the oil and gas layer under dynamic conditions, evaluating the oil and gas layer timely and accurately after encountering the oil and gas display in the process of drilling to obtain a temporary completion test for reservoirs
With the development of technology, DST has been successfully applied in conventional oil and gas reservoirs, high temperature and high pressure oil and gas reservoirs [3,4,5], coalbed methane reservoirs [6,7], high sulfur gas reservoirs and low permeability tight sandstone oil and gas reservoirs [8,9,10,11,12], and achieved good results
Summary
The low-permeability gas reservoirs in China are rich in resources and have great development potential. Many scholars at home and abroad have conducted corresponding research on the production capacity prediction of low permeability gas reservoirs. DST is commonly used in Productivity prediction because of the characteristics of reducing drilling cost, improving oil testing speed and discovering oil and gas layers in time. This paper combines the productivity test data of typical lowpermeability gas fields to predict the productivity of N gas field. N gas reservoir is a heterogeneous gas reservoir with low permeability and thick layers, and the gas reservoir is not fully open, some gas Wells have carried out stimulation operations, and the productivity is difficult to predict. In the N gas field, eight DSTs have been carried out for six layers including H1a, H2c, H3a, H3b, H4b and H5a, which were tested by four wells. The following table explains and analyzes the productivity of the main layer for representative test data
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