Assessment of Carbon Storage in Subsurface Via Well and Seismic Driven Properties of Kadanwari Gas Field Lower Indus Basin Pakistan

Abstract

The Kadanwari Gas Field lies on the Thar Platform of the Lower Indus Basin. It is a mature field: primary recovery is largely complete, but the reservoir–seal pair is still intact and a large body of subsurface data has been collected over its producing life. This makes it a natural candidate for CO₂ storage. Pakistan does not yet operate a CO₂ storage project. The only published storage study at Kadanwari examined a different interval, did not test the bounding faults, and did not derive reservoir properties from seismic inversion. This thesis addresses those gaps by assessing the storage potential of the Lower Goru B sand, the deepest and least studied of the field's sand units, using properties derived from both well logs and two-dimensional (2D) seismic data. The dataset comprises ten 2D seismic lines and three wells. Volume of shale, porosity and water saturation were calculated at each well. Three horizons and the north-northwest to south-southeast trending normal fault system were mapped in time and converted to depth. Model-based acoustic impedance inversion was carried out along the three lines tied to wells, and an Extra Trees regression model trained on the inverted impedance was then applied trace by trace to predict reservoir properties away from the wells. The sealing potential of the bounding fault, F3, was evaluated using a juxtaposition diagram, and storage capacity was estimated volumetrically for each mapped closure. The B sand occurs between 3,438 and 3,462 m depth over a fault-bounded high to the north of Kadanwari-03. All three inverted lines show a laterally continuous zone of low impedance at reservoir level. Along most of its length, fault F3 juxtaposed sand against shale, providing two possible positions along the fault that may act as sealing windows. Storage capacity was calculated from effective porosity, volume of shale and water saturation, together with closure area and reservoir thickness. Assuming a CO₂ density of 600 kg/m³, Closures 1, 2 and 3 hold an estimated 81,968, 167,808 and 326,823 tonnes respectively, giving a combined capacity of 576,599 tonnes (about 0.58 Mt). These figures are static, and apply only to the three mapped Closures. They support treating the closures as preliminary storage targets, with Closure 3 the most promising, but they do not establish either injectivity or long-term containment