Pore pressure prediction using seismic velocity modeling: case study, Sefid-Zakhor gas field in Southern Iran

Abstract

Pore pressure estimation is important for both exploration and drilling projects. During the exploration phase, a prediction of pore pressure can be used to evaluate exploration risk factors including the migration of formation fluids and seal integrity. To optimize drilling decisions and well planning in abnormal pressured areas, it is essential to carry out pore pressure predictions before drilling. Mud weight and fracture gradient are essential parameters to have wellbore stability, prevent blowout, lost circulation, kick, sand production and reservoir damages. Predrill pore pressure accurate prediction allows the appropriate mud weight to be selected and allows the casing program to be optimized, thus enabling safety by preventing wellbore collapse and economic drilling by reducing the cost. The goal of this study is to estimate pore pressure relation with subsurface velocity in the Sefid-Zakhor gas field. Manufactured sonic logs are modified using the check shot interval velocity of Sefid-Zakhor well No. 1. The final acoustic impedance model is converted to the velocity model by removing density. Finally, the velocity model is converted to pore pressure using Bowers (in: IADC/SPE drilling conference proceedings, 1995) relation. The results of the pore pressure model are validated by pore pressure data obtained by the MDT well test tool. Generally, the results show the normal trend for pore pressure in the area, except in the left side of the anticline in the 2D seismic section, because of tectonic uplifting.

Shale Gas Reservoir Pore Pressure Prediction: A Case Study of the Wufeng–Longmaxi Formations in Sichuan Basin, Southwest China

“…For a series of wells in a basin, validation can be accomplished using compressional velocity and by determining the inverted compressional velocity. In this case, the estimated pore pressure gradient trend has opposite distribution characteristics to the inverted compressional velocity, which is consistent with the effective stress theory [1,30]. Therefore, this approach can be helpful when applying the Eaton-Yale process on a basin scale.…”

“…Predicting pore pressure is essential for reservoir characterization, evaluation, drilling operations, and exploitation plans. Determining overpressured intervals is challenging because it is a crucial part of offshore basins' geomechanical and geophysical analysis, especially for unconventional hydrocarbon reservoirs [1]. Overpressures in offshore basins are a common phenomenon and can significantly increase drilling time and cause serious incidents such as blowouts and pressure kicks [2,3].…”

Integrating Petrophysical, Geological and Geomechanical Modelling to Assess Stress States, Overpressure Development and Compartmentalisation Adjacent to a Salt Wall, Gulf of Mexico

“…In many cases, pore pressure must be estimated indirectly, either because the information is required before drilling is undertaken and/or because it cannot be directly measured, especially for lithologies with low permeabilities that would require unfeasibly long measurement times. Estimates and predictions can be made using a range of methods including well log analysis, (Zhang, 2011;Azadpoura et al, 2015;Goulty and Sargent, 2016), seismic interval stacked velocities (Sayers et al, 2002;Brahma et al, 2013;Bahmaei and Hosseini, 2020), and numerical basin modelling (Flemings and Lupa, 2004;Broichhausen et al, 2005;Hantschel and Kauerauf, 2009;Neumaier et al, 2014).…”

Estimation of reservoir porosity using analysis of seismic attributes in an Iranian oil field

“…Well logs and seismic exploration data are commonly used for the evaluation and exploration of hydrocarbon resources (Bahmaei and Hosseini 2019). One of the most important tools for reservoir evaluation and description of reservoir parameters is well log data .…”

“…As a result, prediction accuracy is not only directly related to increased production, but is also critical for enabling more reliable decisions in the field. There are several ways to measure porosity, including well core analysis, microscopic and macroscopic studies, and analysis of geophysical well log data (Bahmaei and Hosseini 2019;Maity and Aminzadeh 2015). In this project, we aim to estimate porosity using seismic attributes.…”