Integration of Conventional Logs, Core, Borehole Images, and 3D Seismic, A Rule of Geological Modeling in Tight Clastics Gas Deep Reservoirs, Oman

Abstract

Integration of conventional logs, core and 3-D seismic with borehole images provide a reliable and decent approach to geological modeling in tight clastics deep gas reservoirs in Oman. The Studied field is of Cambrian-Ordovician age. The field structure is North-South elongated domal anticline associated with a salt pillow. The main hydrocarbon bearing and producing reservoirs are predominantly of continental to marine environments in the deepest part: aeolian dominated formation (A) to sabkha dominated formation (B) in middle intervals and non-marine (coastal plain) to shallow marine (intertidal-subtidal) (C) sandstone members at the shallowest levels. The seismic image quality at the reservoir levels are poor, mainly due to the weak acoustic impedance contrast between deep reservoirs and the overlaying shale, besides the presence of multiple noises further obscured the event, in addition to limited number of core intervals all over the field. In order to refine the structural, depositional model and facies distribution for clastic tight gas deep reservoirs, a detailed integrated borehole resistivity images log interpretation with the available data was performed. Structural dip, structural features like faults locations and their strike and dip angles, sub seismic faults for field transmissibility, and compartments, natural fractures, sedimentological and facies analysis where core - logs comparison was done to improve the rock typing which later correlated to the petrophysical properties, are the major achievements from this study. The study has also analyzed the major accumulations and the paleo-current and paleo wind directions over the reservoirs units by predicting their paleo-drainage and sediments entry points. These results formed valuable input to the field geological modeling. The exercise of tying the above results with seismic data was carried out with a very effective methodology for the generation and significant improvement of a new geological model to support further development and added new reserves in tight gas reservoirs.

Breakouts derived from image logs aid the estimation of maximum horizontal stress: A case study from Perth Basin, Western Australia

“…The latter is generated by applying a colour range to each 1-2-inch-wide moving window from top to the bottom. The detailed processing steps for image logs are provided by Farag et al (2010) and Hurley and Zhang (2011). In these processed formats, the CBIL data can be interpreted for breakouts and to determine the parameters associated with drilling-induced fractures, such as azimuth and strike direction measured throughout the well.…”