Formation evaluation challenges in highly fractured, stacked reservoirs with multiple source rocks and structural complexities which have complicated charging histories, are common in the Middle East. Finding additional pay zones, understanding the contribution of individual oils to the overall production, or evaluating the compartmentalization within the reservoir by resolving the heterogeneity of the reservoir rocks, are to name but a few. This work tries to understand the challenges posed by the sub-surface complexities and attempts to find answers through physical evidence; utilizing both onsite data acquired during drilling and data gathered through organic and inorganic laboratory measurements. Formation evaluation challenges are mostly attributed to formation heterogeneity, which we have aimed to address through the integration of petrophysical and geochemical data within this work. Therefore, a secondary aim of the present paper is to illustrate how such an integrated workflow can bring undiscussed value in terms of improved reservoir management and geological understanding of the field.
This project encompasses the integration of petrophysical and geochemical analyses of the reservoir rocks. Geochemical data have provided the ability to make maturity, richness and other character interpretations and will be combined with important petrophysical properties of the carbonate intervals to predict reservoir heterogeneities. These interpretations could support perforation interval selection on subsequent wells in the field through the understanding of the mobility of the oils, and ultimately impact on production strategies.
Best practices for thermally extracting hydrocarbons from drill cuttings, quality controlling advanced mud gas data and interpretive processes, together with the entire workflow followed, will also be elaborated. The analysis has the objectives of establishing results to support completion decisions through understanding reservoir quality and reservoir fluid heterogeneities specific to the basin studied and the petroleum system in place. The petrophysical reservoir properties such as hydrocarbons in-place, mobility of the oils, porosity, permeability, fracture intensity, geomechanical properties (brittle vs. ductile) and fluid quality assessment in the reservoir will be tied in to geochemical analyses to this extent.
The reservoir properties determination pursued in this study has been carried out using a number of integrated analytical techniques on DST oil samples of six offset wells and rock cuttings, as well as petrophysical logs and advanced mud gas data. The concepts, tools and methods that have been demonstrated for evaluating crude oils, natural gases and petrophysical characteristics of the rocks are applicable to many problems in petroleum production and field development, as well as exploration efforts, and are largely recognized to help reducing the associated uncertainties in a cost-effective manner.