Welltest analysis of hydraulically fractured tight gas reservoirs: a field example from Perth Basin, Western Australia
Hassan Bahrami A , Vineeth Jayan A , Reza Rezaee A and Mofazzal Hossain ACurtin University
The APPEA Journal 52(1) 587-594 https://doi.org/10.1071/AJ11047
Published: 2012
Abstract
Welltest interpretation requires the diagnosis of reservoir flow regimes to determine basic reservoir characteristics. In hydraulically fractured tight gas reservoirs, the reservoir flow regimes may not clearly be revealed on diagnostic plots of transient pressure and its derivative due to extensive wellbore storage effect, fracture characteristics, heterogeneity, and complexity of reservoir. Thus, the use of conventional welltest analysis in interpreting the limited acquired data may fail to provide reliable results, causing erroneous outcomes. To overcome such issues, the second derivative of transient pressure may help eliminate a number of uncertainties associated with welltest analysis and provide a better estimate of the reservoir dynamic parameters.
This paper describes a new approach regarding welltest interpretation for hydraulically fractured tight gas reservoirs—using the second derivative of transient pressure. Reservoir simulations are run for several cases of non-fractured and hydraulically fractured wells to generate different type curves of pressure second derivative, and for use in welltest analysis.
A field example from a Western Australian hydraulically fractured tight gas welltest analysis is shown, in which the radial flow regime could not be identified using standard pressure build-up diagnostic plots; therefore, it was not possible to have a reliable estimate of reservoir permeability. The proposed second derivative of pressure approach was used to predict the radial flow regime trend based on the generated type curves by reservoir simulation, to estimate the reservoir permeability and skin factor. Using this analysis approach, the permeability derived from the welltest was in good agreement with the average core permeability in the well, thus confirming the methodology’s reliability.
Hassan Bahrami is a PhD candidate in the Department of Petroleum Engineering at Curtin University, and is now focused on tight sand gas reservoirs’ damage and productivity. Prior to Curtin University, he worked for Schlumberger Data and Consulting Services (DCS) as a borehole reservoir engineer (2003–09), and at Tehran Energy Consultants as a reservoir engineer (2001–03). Hassan holds a BSc in chemical engineering from Persian Gulf University, and an MSc in reservoir engineering from Sharif University of Technology, Tehran, Iran. Hassan.Bahrami@postgrad.curtin.edu.au |
Vineeth Jayan is a petroleum engineer from Curtin University in Perth, WA. He is now working for Santos Limited in the GLNG project, based in Brisbane. Before joining Santos in September 2011, he completed his Masters degree in petroleum engineering at Curtin University. Prior to this, he worked for TATA Consultancy Services, India as an assistant systems engineer (2006–09). Vineeth also holds a Bachelor degree in mechanical engineering from University of Kerala, India. Saachin2005@yahoo.co.uk |
Reza Rezaee is an associate professor at Curtin University’s Department of Petroleum Engineering, and has a PhD in reservoir characterisation. He has more than 20 years’ experience in academia and industry. During his career he has been engaged in several research projects supported by national and international oil companies. With his supervisory work at various universities, these commissions have involved a wide range of achievements. He has supervised more than 50 MSc and PhD students during his university career to date. His research has been focused on integrated solutions for reservoir characterisation, formation evaluation, and petrophysics. He has used expert systems such as artificial neural networks and fuzzy logic, and has introduced several new approaches to estimate rock properties from log data where conventional methods have failed to succeed. He is now focused on unconventional gas, including gas shale and tight gas sand studies, and is the lead scientist for the WA:ERA (EIS) Tight Gas and Shale Gas research projects. R.Rezaee@curtin.edu.au |
Dr Mofazzal Hossain is a senior lecturer, postgraduate course coordinator, and SPE faculty advisor at the Department of Petroleum Engineering in Curtin University. He has more than 14 years of experience in teaching, research and consulting work, with a major focus in the areas related to well technology and petroleum production technology. He has worked with the University of Adelaide and UNSW, Saudi Aramco and the King Saud University in Saudi Arabia, and the Reservoir Engineering Research Institute (Palo Alto). His research and works encompass reservoir stimulation by hydraulic fracturing for improved production from unconventional tight/shale gas reservoir, completion optimisation, rock fracture mechanics and wellbore stability. Dr Hossain received his PhD in Petroleum Engineering from UNSW. Member: SPE and IEA. Md.hossain@curtin.edu.au |
