A Study on Optimization of CBM Water Drainage by Well-Test Deconvolution in the Early Development Stage

Abstract

Different from the conventional gas reservoir, coalbed methane is developed mainly by water drainage, which leads methane desorption after reservoir pressure drop. Water drainage at a reasonable speed in the early development stage is the key for enhancing later gas performance. Therefore, the investigation radius, which reflects the pressure drop region scale, is studied by deconvolution well-test to find the reasonable water drainage speed in the early period. First, the early production data (well-bottom pressure and water rate) are processed by deconvolution algorithm, and then the pressure data under unit rate is obtained to invert the comprehensive reservoir permeability and investigation radius. This deconvolution method can save the cost of the conventional well-test, and avoid reservoir damage caused by frequent well shut-off. The feasibility of the deconvolution test method is verified by comparing its interpretation results with those of the conventional pressure drop/build-up test. For a field application, the 29 wells’ comprehensive permeability are inverted by the deconvolution well-test using early water production data of Hancheng block. Furthermore, their investigation radius and pressure drawdown gradient are calculated, and the performance optimization is determined by relationship analysis between working fluid level and steady gas production rate. We find that well-bottom pressure and reservoir pressure should decrease steadily in the early development stage, with the working fluid level declining less than 1 m/d (1 m per day) in wellbore, and the pressure drawdown gradient declining less than 2.8 MPa/100 m.

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An Empirical Study on Big Data Model and Visualization of Internet+ Teaching

“…In the course, the teacher speaks fluently, slowly, and clearly, which is a positive model for the students' oral learning. At the bottom of the video, there is a "speed adjustment" function, so students can adjust the teacher's speech speed according to their needs, which is a kind of personalized setting [18]. Also, the intonation of the teacher is lighter and heavier, so that students can pay attention to the points when they need to emphasize them.…”

Photothermal Effect: The Amygdaloidal Nano-Structure Based on Bi2S3 for the Enhanced Degradation of Rhodamine B Under Irradiation by NIR

“…As indicated by the temperature change curves from Figure 4C, the photothermal conversion performances of these Bi 2 S 3 NPs were tested through exposure to irradiation with an 808 nm laser for 5 min at a power intensity of 1 W cm −2 . The efficiency of light-toheat was counted as 24.7% by using an established method (Gao et al, 2018;Tsai and Ma, 2018). The temperature of the Bi 2 S 3 NPs solution was added from 23.2 to 30.3°C at the same time.…”