PROPERTIES OF FOAMED CEMENT WITH ADDITIVES FOR ZONAL ISOLATION IN COAL BED METHANE (CBM) WELLS (A CASE STUDY ON MUKAH COALFIELD, SARAWAK)

Coal bed methane (CBM) generally has lower fracture gradient as compared to
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conventional oil or gas wells due to weak structures of coal. Therefore, CBM are more
vulnerable to downhole problems faced such as lost circulation and formation fracture as
the formation cannot withstand the cement densities of averagely above 11 ppg
(1320kg/m3
). Foam cement when used together with additives offers a versatile and
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economical means of cementing with low density (5-13 ppg) and high strength per unit
volume. Foamed cement was first introduced in the application of light weight cement for
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use in constructions and site building, which later, similar theory were applied in the
foamed cementin~ process for the oil and ~as industry. The objectives of this project are
to determine properties of the foamed cement when used with Microsilica and BJ Ultra
additives (density, compressive strength, fluid loss, porosity and permeability) to be
compared and analyzed for their compatibility for the Mukah Coalfield, Sarawak. This
thesis will discuss the characteristics of CBM reservoirs, foamed cement with additives
sample preparation methods and data analysis. The various aspect of slurry design,
including their method of determination is discussed. The properties of the conventional
Class G cement can be determined directly with existing equipment which includes the
curing chamber, compressive strength testers, and HPHT Filter Press. For the foamed cement, since these parameters are determined by the air quality and water to cement
ratio and type of additive used, their relationships to density are focused.