Petrophysical and Geochemical Analysis of Chichali Formation for the Source Rock Evaluation: A Case Study of Chanda-01 Well, Upper Indus Basin, Pakistan

Abstract

A source rock has the ability of generating hydrocarbons after the maturation of the organic component for a
specific period of time. The hydrocarbon generation and release from a potential source rock is dependent on the
content of the organic matter, which is determined by Total Organic Carbon (TOC) content. In this research, the
Chichali Formation of Cretaceous age is considered to be a source rock in the Chanda gas field, Upper Indus Basin on
the basis of petrophysical and geochemical results of well Chanda-01. The study includes computation of TOC,
mineralogy and parameters like porosity, permeability and fluid saturation which have been carried out from Well log
data. Additionally, geochemical results of the well have been incorporated in order to calibrate and authenticate both
results. The formation is encountered at a depth of 4543 m in Chanda-01 well and its thickness is about 34 m. The
formation has been divided into two parts on the basis of lithology. The upper part is representing sandy shale, whereas
the lower part exhibits massive shale unit. The log data of natural gamma ray, resistivity, density and spectral gamma
ray, including uranium, thorium and potassium curves have been interpreted in the lower part of the formation, which
confirms that the formation is possibly deposited in anoxic conditions with sufficient organic rich content. Moreover,
geochemical analysis of the rock cuttings of the well shows good Vitrinite Reflectance and TOC results which
complement the results obtained from the petrophysical analysis. Seven rock samples of Chichali Formation have been
analyzed for its TOC & VR value which confirms that shale in this area has fair source potential as the average value of
both tests against these samples are greater than 1%. Therefore, having fair source rock potential in Chanda gas field,
there is a possibility that Chichali Formation could be a potential source in the other fields of Upper and Middle Indus
basins and a prospect for the shale gas resource as well.
Keywords: Chichali Formation, source rock evaluation, total organic carbon, DlogR technique.