Recent trends in petroleum production have focused on developing unconventional gas reservoirs such as tight gas and shale gas. Considering worldwide shale gas resource potential, the largest resources exist in the former USSR and in North America, while for China, Central and Southeast Asia the estimated shale gas resource is 1115 TCF. Despite the smaller resource projection, this unconventional resource is of great interest for future development. In Thailand, the primary energy source is oil and natural gas, with 77% of electricity generated from natural gas (EIA, 2011). Yet current production is not enough to support the growing energy demand in Thailand, and there is increasing emphasis in exploring potential unconventional resources to meet this demand.
A study has been conducted to improve reservoir knowledge of the Huai Hin Lat formation, believed to be an important source rock for the gas fields in northeast Thailand. The Huai Hin Lat formation consists of fluvio-lacustrine sediments of Late Triassic. The formation is exposed along the margin of the Khorat Plateau. Petroleum exploration in Khorat Plateau has been ongoing since 1962 and two gas fields have been discovered and commercially produced in the Khorat Plateau since 1988.
Seven shale samples were taken from the Huai Hin Lat formation. All samples are the organic rich fine-grained rocks. The MicroCT technique was measured for porosity parameter. The average porosity of the samples was approximately 4.9%, and a pore size distribution was found. In addition, geochemical analysis was performed to determine total organic content (TOC) of the shale samples. The average TOC was found to be approximately 4.9%.
Permeability was measured for the seven samples using transient pressure pulse decay. The permeability range of the samples was found to be 90 (D to 280 (D and the average permeability of sample was approximately 180 (D. Permeability varies significantly because the shale is somewhat heterogeneous. Natural fractures present in the formation may also affect the value of effective permeability.
This paper provides details regarding the analysis of the Huai Hin Lat samples and the shale's rock properties as they relate to other commercial unconventional gas resources. The work is significant because there are few existing petrophysical evaluations of this formation. Results from this study will identify and highlight key reservoir parameters necessary to further assess the commercial potential of the Huai Hin Lat shale as a shale gas reservoir.