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ABSTRACT

During the production period of methane gas from the coalbed methane

(CBM) well, an artificial lift is used to increase the water rate with the target of

reducing the reservoir pressure until it reached the critical desorption pressure so

that the gas can detach itself from the surface of the coal formation. The artificial

lift being used is the progressive cavity pump (C). The data gathered to ma!e

the C design is from the CBM "# well.

The results that is e$pected from designing the C is %M, tor&ue, a$ial

load, tensile strength and horsepower. 'rom those results, it is e$pected that the

design can be adusted and optimised for the dewatering process of CBM "#

well. The re&uired data that is needed for the C design are pump set depth,

initial reservoir pressure, well head pressure, water rate, fluid density, fluid

viscosity, tubing sie, rod sie and rotor sie.

The C specification must be chosen accurately based on the reservoir

capability to channel fluids. 'or CBM "# well, the critical desorption pressure is

*+ psi. The water rate is -/ bpd when the bottom home pressure is at 0// psi.

The pump with displacement rate (D%) *bpd1%M can carry the re&uired water

rate with only +23 %M. 4owever, using this specification for the pump will only

last for months because of the overstress e$perienced by the pump based on the

value of tor&ue, tensile strength and a$ial load that is huge. 5n the other hand,

using a smaller displacement pump will cause it to have to be replaced fre&uently.

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"nother variable that can be analysed are rod string design and surface

driver design. By replacing the pump and rod string will increase the life time of

the surface driver. The smaller the D% in the pump, the smaller the energy

re&uired by the surface driver to operate the pump, hence enhancing the durability

of the driver.