Pore Pressure Prediction in Unconventional Carbonate Reservoir

Abstract

Prediction of the formation pore pressure is considered as a significant simulation process during the drilling and production phases of the carbonate reservoir. The deficiency in this prediction allows for the occurrence of many troubles like blowouts, kicks, hole washouts, wellbore breakout, and stuck pipe. The most common conventional methods for the pore pressure prediction are Eaton's and Bower's methods which depend mainly on the normal compaction trend and commonly applied on Shales. The objective of this work is the prediction of the formation pore pressure by the application of the modified Atashbari prediction model upon the wireline logging data. This method depend on the porosity and the compressibility attribute of the rocks for the estimation of the pore pressure without any need for the normal compaction trends. The method was applied on the carbonate reservoir of the Middle Eocene Apollonia Formation, Abu El-Gharadig basin, Egypt. It is a gas bearing reservoir which characterized by its high porosity and low permeability. The results were compared with the other commonly used methods and show an improvement in the pore pressure estimation. It can be used as an individual method or in complement with other available methods.

Polygonal faults in Eocene carbonate reservoir, Abu El‐Gharadig Basin, Egypt

“…Stewart (1999) suggested that gas accumulations at shallow depths can cause enough overpressure to form set of faults and fractures with a circular structure. An important observation, however, is that the chalk reservoir of the Apollonia Formation is characterized by its low formation pressure (Elmahdy et al, 2018;Salah et al, 2016) which suggests the releasing of the formation pressure after the generation of the polygonal faults.…”

“…The Apollonia Formation (upper Paleocene to middle Eocene) is overlain by the Dabaa Shale (Oligocene), and is underlain by the chalk of the Khoman Formation (Upper Cretaceous) ( Figure 3). The Apollonia Formation was studied in detail in terms of its lithology, palaeontological characteristics and reservoir productivity (e.g., El-Bendary et al, 2016;Elmahdy, Farag, Tarabees, & Bakr, 2018;Salah, Orr, Abdel Meguid, Crane, & Squires, 2016;Sedek & Al Mahdy, 2013;Sousa & Badri, 1996).…”

“…Here, the Apollonia Formation is divided into four members (A, B, C and D): members A and C are mainly composed of carbonates, while members B and D are mainly shales (Figure ). In the A3 and A5 layers of the Apollonia A member, an unconventional gas‐bearing chalk reservoir with high porosity (15–40%) but low permeability (0.01–0.90 mD) (Elmahdy et al, ) was discovered by Shell in 2007.…”

Estimation of Rock Mechanical Parameters Using Well Log Data in the Well Poseidon 1, Lower Cretaceous, Browse Basin, Northwest Shelf, Australia

“…In order to estimate the in-situ stresses, several calculations were carried out with two types of calibrations on them. For the overburden, the density all over the overlying strata (shallow and not available in the logs) was extrapolated using a tie in the mudline [20] and the vertical stress integrates the effects of the water column with a fixed water density [1]. The pore pressure used was calculated from the Sonic Eaton model [21] and the normal pore pressure method [1], these calibrated with Modular Formation Dynamic Tester (MDT) data [22].…”

Detection of Over Normal Pore Pressure Intervals by Using Well Logs

“…[2]. Pp estimation is based on Terzaghi principle and Biot law, where they are dealt with estimation of effective stress according to determined Pp, as well as, they accounted source of up-normal (over and under) pressure as disequilibrium compaction criteria [3].…”