A production type-curve solution for coalbed methane reservoirs

Parameters controlling high-yield coalbed methane vertical wells in the B3 area, Xishan coal field, Shanxi, China

“…As shown in Figure 12(d), the relation between reduced water level and gas production in the east and west subareas exhibits opposite trend. The reduced water level in the west subarea ranging from 600 to 1000 m has negative effect on gas production, which is in line with the results of other scholars (Aminian and Ameri, 2009; Ghaedi et al., 2015; Thararoop et al., 2015). However, in the east subarea, most of the high yield wells tend to locate in high reduced water level (average is 1010.7 m) section.…”

“…However, single-peak type is induced by fractured process, so they have transient time of high gas production during the early stage of gas production. Undulant type always has relatively heavy stress sensitivity, which is harmful for coal reservoir and gas production (Thararoop et al, 2015).…”

“…However, single-peak type is induced by fractured process, so they have transient time of high gas production during the early stage of gas production. Undulant type always has relatively heavy stress sensitivity, which is harmful for coal reservoir and gas production (Thararoop et al., 2015).

Figure 4.Typical shapes of CBM production curve types in the B3 area: (a) increasing type, from well C143; (b) double-peak type, from well C025; (c) single-peak type, from well C035; and (d) undulant type, from well C058.

…”

A New Approach to Evaluate and Predict the Reservoir Performance of a Two-Phase Flow Coalbed Methane Well with Fully Coupled Time-Dependent Desorption and Pressure-Dependent Diffusivity Effects

“…King was among the first to formulate the CBM mass balance equation by introducing the Z * function, which enables the feature of a linear trend of with cumulative gas production similar to conventional gas reservoir behavior. Later on, a modified approach was developed to improve upon the King method with an assumption of constant water saturation throughout the life of the well for determination of original gas in place, drainage area, and initial reservoir pressure. , The two phase flow effects and equilibrium desorption effects in CBM wells have been conceptualized by a few researchers in the form of pseudo-pressure functions and type curves. , Salmachi and Yarmohammadtooski extended the pressure derivative technique in production data analysis to describe the flow equation under constant and variable bottom-hole pressure conditions. Though these models captured the macropore transport mechanism and micropore desorption characteristics of CBM reservoirs, the aspect of pressure-dependent diffusivity due to changing effective stress conditions and coal matrix shrinkage effects was missing in the above studies.…”

“…5,6 The two phase flow effects and equilibrium desorption effects in CBM wells have been conceptualized by a few researchers in the form of pseudo-pressure functions 7 and type curves. 8,9 Salmachi and Yarmohammadtooski 10 extended the pressure derivative technique in production data analysis to describe the flow equation under constant and variable bottomhole pressure conditions. Though these models captured the macropore transport mechanism and micropore desorption characteristics of CBM reservoirs, the aspect of pressuredependent diffusivity due to changing effective stress conditions and coal matrix shrinkage effects was missing in the above studies.…”