Cleat Orientation from Ground Mapping and Image Log Studies for In Situ Stress Analysis: Coal Bed Methane Exploration in South Karanpura Coalfield, India

Abstract

Conventional well logs from three wells in South Karanpura coalfield are analyzed to correlate 10 major coal seams belonging to the Barakar formation for coalbed methane (CBM) exploration. Face cleat orientations are studied for the Simana and Argada coal seams from the Sirka and Argada mines. It varies from 130 to 140°N for a total 349 face cleats observed from Simana and Argada coal seams. Cleat identification and its orientation have also been analyzed from simultaneous acoustic and resistivity (STAR) log from two CBM wells located 20–22 km away from the Sirka and Argada mines. Total number of fractures is found to be 1118 from two wells. Face cleats are not distinguishable from STAR image. Fracture density in coal is varying from 2.48 fractures per meter to 23.8 fractures per meter with a maximum density in the Banasgarah seam. Fracture orientations observed in Saunda, Sayal, Balkudra, Kurse, Hathidari, Banasgarah, and Argada vary from 10°N to 115°N. The in situ maximum horizontal stress (S H) is computed from azimuthal anisotropy data, using a cross-multipole array acoustic (XMAC) log from a well. Azimuthal anisotropy ranges between 3.5% and 7.6%. The S H orientation varies from 110°N to 115°N. It is observed from the XMAC azimuthal anisotropy analysis that the orientation of S H in the Argada seams varies from 110°N to 113°N. The 163 face cleats in Argada seams at Argada are oriented toward 135°N–140°N. This indicates that the face cleats are aligned parallel to subparallel with the S H direction. Good fracture density, open fractures/face cleats toward S H are to be useful for CBM extraction from these wells.

Anisotropy analysis for optimized gas production in Coalbed Methane reservoir, Bokaro field, India

“…In the image log, drilling-induced fractures (DIFs) and borehole breakouts (BOs) are the indicators of the present-day stress direction (Barton et al 1998;Barton and Zoback 2002;Ali et al 2017). BOs corresponds to the Sh direction occurs due to low mud weight, is not observed in this study whereas DIFs are observed as a thin vertical pair of line at 180° apart in image log, correspond to the SH direction which occurs due to high mud weight (Bell and Gough 1979;Trautwein-Bruns et al 2010).…”

Postfracturing permeability prediction for CBM well with the analysis of fracturing pressure decline

“…In‐situ stress has great influence on the original cleats orientation and permeability of coal reservoir, as well as hydraulic fractures of CBM wells . If the coal is considered to be homogeneous, continuous, and isotropic, the hydraulic fractures will first crack in the direction that is perpendicular to the minimum horizontal principal stress.…”

Characteristics of in situ stress and its influence on coal seam permeability in the Liupanshui Coalfield, Western Guizhou

“…6 The current in situ stress regime is not only one of the main parameters affecting the construction effect of hydraulic fracturing, but also an important factor affecting reservoir fluid migration and accumulation. 4,[7][8][9] Therefore, in the initial stage of CBM development in China, 10,11 using various methods to better understand in situ stress is an effective means of CBM exploration and development. 12 At present, the commonly used methods for in situ stress measurement include mechanical methods, geophysical methods, and geological methods.…”