Reservoir rock study of the Sam Khaen Conglomerate Member, Huai Hin Lat Formation, Sap Phlu Basin, Nakhon Ratchasima, Thailand: implications for rock mechanical properties

Abstract

Demand for commercial energy of Thailand has continuously increased and proved reserves (P1) of natural gas will be consumed within only next 11 years. If there are additional data of exploration and drilling, probable (P2) and possible (P3) reserves including undiscovered total petroleum initially in place (PIIP) could be developed to P1 and will last a further 30 years. One area with high potential is the Huai Hin Lat Formation, Sap Phlu Basin, that the Khlong Muang section was studied. It is 29 m thick correlating to a part of the Sam Khaen Conglomerate Member and was divided into under 2, 2–4, and over 4 cm pebble sizes. Six samples were measured their matrix area percentage by using planimeter, rock mechanical properties following ASTM D7012-14, and rock-forming elements and minerals obtained by XRF and XRD methods. The matrix areas range from 1.47 to 24.88% of smaller- to larger-grained samples. Conformably, grain and matrix are composed of calcite and quartz of brittle minerals that are easily fractured or rephrased with compressive strength of around 78 MPa. Moreover, Al₂O₃ was detected that probably belongs to clay minerals and gradually increases from smaller- to larger-grained samples. As a result, Young’s modulus, Poisson’s ratio, and compressive strength of Beds 20 and 24 and Beds 4 and 18 are the lowest (5.48 MPa, 0.115, and 41.41 MPa) and the highest (11.69 MPa, 0.172, and 69.16 MPa). Therefore, rock mechanical properties are associated with rock-forming minerals of grain and matrix as well as their area percentages.