Seismic and Well Logging Data Interpretation for Reservoir Properties Estimation at Beni Suef Oil Field, Egypt.

Abstract

The present work was devoted to evaluate the reservoir properties for Beni Suef Oil Field. Beni Suef Oil Field is located in the Western Desert, and covers the western part of Beni suef Basin. It is restricted between latitude 29 º 00' N and 29 º 87' N and longitudes 30º 30' E and 32º00' E. The seismic interpretation, well log analysis and formation pressure evaluation are used to define the subsurface geological structure and the petrophysical properties favoring for the oil accumulation of the hydrocarbon materials and they are also used to determine reservoir driving mechanisms and fluid migration paths that control the behavior of fluids within reservoir. Such work was conducted through several steps, started by reviewing the geologic setting of the study area to shed lights on the subsurface geology, subsurface stratigraphy, and tectonics. Seismic interpretation performed in the study area for twenty-eight seismic lines in both strike and dip directions to identify the subsurface structure for the tops of Formations of interest (Abu Roash, Bahariya and Kharita Formations). Close investigation of these sections show that the area is affected by a group of normal faults with different trends and throws. These faults form together horsts and grabens structures. The well logging analysis carried out for six wells in the study area by using a petrophysics computer program (TechLog 2011) developed by Schlumberger. The procedure includes the determination of water resistivity by using Pickett crossplots, Rwa and SP methods.. The volume of shale (Vsh) is calculated by using GR log as a single indicator and Neutron-Density log as a double indicator. Also, the corrected porosity was calculated by: Sonic, Density and Neutron logs. Formation pore pressure calculated by several methods: pre-drilling method using seismic velocities, during drilling method using d-exponent and after-drilling method using well logs data. As the formation pore pressure estimation is very important for drilling and reservoir engineers and if it predicted or calculated well it will help in avoiding many problems like well kicks, lost circulation, blowouts, stuck pipe, excessive costs and borehole instability. In this work we do not have measured RFT data so we used several methods for calculating the formation pore pressure: 1) before drilling using seismic velocities, 2) during drilling using drilling and mud parameters, and 3) after drilling using nearby well logs data. The pre-drilling methods which are used for predicting the pore pressure are: the equivalent depth method, Eaton method and modified Eaton method. All these methods require knowledge of the interval velocities that were calculated from the available root mean square velocities. Also, the available drilling parameters (rate of penetration (ROP), weight on bit (WOB), rotary speed (N), bit diameter (db), Formation fluid density and mud density) used for calculating the formation pore pressure during drilling. Also, we used the nearby measured well logs as porosity logs for calculating the formation pore pressure. Pore pressure gradient maps constructed for Abu Roash and Bahariya Formations that exhibits the locations of both higher and lower pressure gradients to predict the possible horizontal fluid flow (migration paths) for the proposal of new prospects. Finally, it is possible to calculate and recommend the required heavier mud weight to drill.