In-situ stress, Pore Pressure and Geomechanical Modeling: An Aid to Reservoir Exploration and Development in the Krishna-Godavari and Upper Assam Basins, India

2018 Honorary Lecturer
South and East Asia

Rima Chatterjee

Indian Institute of Technology (Indian School of Mines)
Dhanbad, India

Summary

Comprehensive geomechanical modeling of subsurface reservoirs requires knowledge of rock strength, pore pressure, magnitude and orientation of principal stresses. This study provides analyses of in-situ stress and pore pressure in several oil/gas fields of Krishna-Godavari basin. High pore pressure gradients varying from 11.85 to 12.80 MPa/km exist within these oil/gas fields. Vertical stress (SV) gradients in the range 21.00 to 22.85 MPa/km are seen to exist. Minimum horizontal principal stress (Sh) magnitude is found to vary from 64% to 76% of the SV while maximum horizontal principal stress (SH) magnitude is observed to vary from 90% to 92% of SV within normally pressured to over-pressured sediments. The breakout derived SH orientation from two wells varies from N14°E to N22.5°E in the Krishna-Godavari basin.

With growing interest in small field reservoirs we venture into more and more difficult reservoirs every day. The need to understand the geomechanical properties of the target environment is becoming increasingly important to both drilling and completion operations. Adequate well placement, design, construction, completion and prospect definition must begin with a geomechanical earth model of the target area. This can be only done through complete understanding of pore pressures and in-situ stresses. Conventional well analysis, local geology, seismic velocities and basin knowledge can be used to resolve the key pressure generating factors, such as the rates of deposition and compaction that can be responsible for the generation of abnormal subsurface pressures. With quality seismic volumes, a seismically-derived pore pressure model can be generated that is integrated into the log and model calibrated with direct measurements of pressure, in situ stress, and observations to understand wellbore behavior. This approach helps to ensure that the analysis honors all available petrophysical, geophysical, and geological information, providing a robust and reliable prediction of subsurface pressure, in-situ stresses and wellbore stability for the target well location. Two-dimensional (2D) stress modeling using finite element analysis has been carried out for some important oil/gas fields situated within East and West Godavari sub-basins as a part of the current study. Discontinuities in the stress pattern which can be associated with interfaces between weak and competent layers have been commonly observed and especially where silici-clastic and volcanic inter-bedded sequences are encountered. The model predicted stress orientations are verified with the Formation Micro Imager (FMI) log data of wells at the above mentioned sub-basins. Using the poroelastic model, the minimum and maximum stress in the Upper Assam basin’s tectonically active portion of north-east India, have been derived. This can be uniquely characterized by the presence of normal as well as reverse faulting regime in the same basin.

Biography

Chatterjee

Prof. Rima Chatterjee received a gold medal in her master’s degree in Applied Geophysics from Indian Institute of Technology (Indian School of Mines), Dhanbad, India. Born in India, Chatterjee completed her bachelor’s degree with honors in Physics. She received her PhD from IIT(ISM), Dhanbad working on ‘Well Log Analysis and Stress Studies in Hydrocarbon Exploration” in 2003.

Prof. Chatterjee is a major contributor in the World Stress Map project from India and was invited to the 3rd World Stress Map Conference at Potsdam, Germany. She has done exemplary work on stress studies in Mahanadi, K-G, Cauvery and Upper Assam basins. She has worked on CBM reservoir characterization in Jharia, Raniganj, South Karanpura and Bokaro coalfields. She has a lot of experience on working on coal log analysis for coal quality estimation in Korba and Bishrampur coalfields. She has published a good number of research papers in EPSL, GRL, Marine Geology and the AAPG Bulletin as well as other reputed journals. She attended many National and International Conferences in India and abroad. Working under her guidance six students have been awarded PhD degrees and over a hundred have completed their dissertation program at the Masters level. As a faculty advisor of SEG Student Section, ISM, she has organized many workshops as well as a Student Interaction Programme under the banner of SEG Student Section, IIT(ISM), Dhanbad. She has also successfully organized professional courses on geomechanical studies on well bore stability and rock physics modelling and mining safety for which she has been highly applauded.

Schedule

Date Location Host
26 Feb Bandung, Indonesia University of Padajaran Student Chapter
27 Feb Bandung, Indonesia Institute of Technology Bandung Student Chapter
28 Feb Depok, Indonesia     University of Indonesia Student Chapter
1 Mar  Surabaya, Indonesia     Institute of Teknologi Sepuluh Nopember Student Chapter
3 Mar  Yogyakarta, Indonesia University of Pembangunan Nasional Veteran
Joint Meeting with
University of Gadjah Mada Student Chapter
5 Mar  Jambi, Indonesia  University of Jambi Student Chapter
7 Mar  Makassar, Indonesia    University of Hasanuddin Student Chapter
8 Mar  Semarang, Indonesia   University of Diponegoro Student Chapter
10 Mar Bandar Lampung, Indonesia University of Lampung Student Chapter
20 Mar Varanasi, India Banaras Hindu University
26 Mar Hyderabad, India National Geophysical Research Institute (NGRI)

Please check back for lecture locations and dates in India

SEG Honorary Lecturers
Sponsored by:

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