Coal Bed Methane (CBM) has become one of the most important unconventional resources for today petroleum industry since its discovery in many countries including Indonesia. The main challenge for CBM fields is a proper reservoir characterization in coal matrix, cleat and shale layers. Another main challenge is a variation in reservoir productivity from zone to zone. Formation evaluation for this unconventional reservoir is not as straight forward because the evaluation program needs to be adjusted to obtain enough reservoir information for an effective field development plan.
The Dual Packer Formation Testers (FT) can be used to test zones where matrix porosity is too low for a single probe FT such as carbonate and fracture basement reservoirs. However, the use of dual packer FT remains quite a challenge due to time per station, tool sticking risk, and limited packer intervals. This paper reviews the use of Dual Packer FT to evaluate reservoir properties in one of the CBM wells in Asia.
This paper presents the use of Dual Packer FT for an Interval Pressure Transient Test (IPTT) for reservoir pressure, fluid sampling, zone permeability, and also for a stress testing applications. This paper will be more focused on the stress testing technique using Dual Packer FT. This "micro-frac" application in CBM wells plays an important role in providing shale layers' stress parameters such as a fracture treatment design and an optimal completion design. However, it also has its operational challenges associated for pre-job planning.
This paper presents a systematic integration between pressure transient analysis and fracture diagnostic plots utilizing a G-function plot, as well as a Square-Root time plot in this smaller scale of fracturing operations. The output of the analysis including initial breakdown pressure, closure pressure, fracture propagation pressure, initial shut-in pressure, and shale permeability will be discussed and compared with full scale fracturing, drilling leak off tests, and modeling results from geomechanics study. This paper will also address technical and operational aspects of the Dual Packer FT operation in this unconventional reserve.
