Seismic, structural and petrophysical modeling of Badin IV block, lower Indus basin, Pakistan (T-1506) (MFN 4305)

Abstract

Badin IV South block is located in Thatta-Hyderabad-Mirpurkhas Districts of Sind Province and is 200km away from Karachi. It covers the area of 1265.3 km2. It is bounded by latitudes 24 °50′ - 25 °25′ N and longitudes 68 °21′ - 69 °20′ E and is a part of the Badin platform which lies in the Lower Indus basin. . The Nagar parker Granite is exposed in the South-eastern side of the block. Badin block merges into Kirthar and Karachi Trough on the western side. On the northern side the Mari-Bugti Inner Folded zone is present. The study area is dominated by normal faults and negative flowers structures due to extensional and Trans tensional forces. The data obtained for the seismic interpretation, petrophysical evaluation and petrophysical modeling included seismic lines of PK-92 and PK-94 vintage and log data of wells Doti-01, Mehro-01, Gadap-01, Pirshah-01and Beghari-01, which was released by the Landmark Resources with prior approval from the Directorate General of Petroleum Concession for carrying out this study. Major purpose of the study is to investigate the reservoir properties and geometry on the basis of structural modeling and property modeling processes and also to look into the reasons for well failure in the area. Specific fault behavior and geometry is established on the basis of 3D fault modeling. The role of faults is significant in this area because the structures are generally fault bounded with associated dip closures. As fault pattern is quite complex in this area due to several tectonic episodes, the fault modeling process lead to the better understanding of the structural geometry and its extents etc. This investigation encompasses conventional seismic interpretation which involves the seismic to well tie followed by horizon tracking, fault identification and marking. Different reservoir properties like porosity, water saturation, hydrocarbon saturation, are computed from the blend of different wireline logs. Consequences to the above revealed processes lead to a better and more commonsensical understanding of depositional and structural models, using the yield from above mentioned processes a 3D model is generated. Prior to that is the petrophysical evaluation process and upsacling of different properties were carried out. After the 3D modeling process and petrophysical evaluation and upscaling is completed, different reservoir properties are populated into the model. The results of property modeling, and fault modeling is amalgamated together to get a static model and a property populated static model of the reservoir.Four Horizons are marked which are Sand-A, Sand-B, Sand-C and Chiltan Limestone. Normal faults and negative flower structures are identified, which extended through all these formations. Time contour maps are generated for these above mentioned horizons. Depth contours are then generated with the help of these contour maps which delineated the subsurface structures and the tectonic activities which took place throughout the geologic past. Petrophysical evaluation of the wells revealed that all wells are water wet and the porosity of reservoir sands of the Goru Formation ranges from 15% to 20% and saturation of water ranges from 95% to 100%. 3D static model is generated and later on populated with porosity which reveals that Sand-A truncates eastwards and all sand units of the Goru Formation have good porosities in central, eastern and northern parts of the study area while in the west quality of sand is not good enough to be categorized as reservoir.