A New Rock Type Based Evaluation Method for Unconventional Reservoirs
Date: January 24, 2017
Time: 11:30 am -1:00 pm
Location: BP Plaza, Westlake 1 - Pondview 1 & 2
501 Westlake Park Blvd, Houston, TX 77079
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Time: Lunch 11:30, Presentation at 12:00
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Speaker: Robert Lieber, Corsair Petrophysics
“A New Rock Type Based Evaluation Method for Unconventional Reservoirs”
The use of measured capillary pressure curves to determine saturation based on height above free water level has long been used as the best in class analysis methodology for understanding hydrocarbons in place as well as reservoir deliverability in conventional reservoirs. The use of rock types, each with a unique capillary pressure relationship, is the preferred method of capturing reservoir heterogeneity and for computing irreducible water saturation for the creation of static and dynamic reservoir models. In unconventional reservoir, this approach has proven more challenging as fluid saturation is not controlled by the current rock based measured capillary pressure relationships. This has led to the industry, for the most part, to use more electrically based analysis (such as embodied in the Archie relationship) even though the rocks being analyzed do not fit the characteristics in a classic Archie rock type. Also these conventional work flows ignore fine-scale variations in rock properties that are well documented in unconventional reservoirs which are well below log resolution. This paper proposes a methodology where unconventional rock types are defined by clay volume, porosity, and water saturation based on core measurements that more accurately represent the storage capacity of these reservoirs. While the rock type approach is very core dependent, the industry has gathered tremendous volumes of core data which for the most part is highly underutilized once an initial reservoir evaluation has taken place. This method does require that we gather more core data, but rather that we use our existing data more rigorously. The issue of matrix deliverability is discussed, but until the physics of fluid flow in nano-pore systems is better understood prediction of matrix efficiency will remain an enigma. The use of a rock type based method for unconventional reservoirs allows a better predictive ability for field wide hydrocarbon pore volumes since rock types are based on depositional and digenetic processes which are at least partially understood rather than simple trend maps based on calculated porosities and fluid saturations which depend on assumptions which are not based on any relevant physical understanding. Adoption of this new approach will lead to improvement of our understanding field wide productivity and allow for the delineation of sweet spots essential for the economic viability of unconventional reservoirs.
Biography: Robert Lieber is astrophysicist with over thirty-five years of varied petrophysical experience in domestic and international offshore and onshore basins with a focus on challenging reservoirs. Bob has split his career between operating companies and consulting activities from supermajors to one-off consulting projects. Bob is currently with Corsair Petrophysics as a consulting petrophysicist where he splits his time between technical activities and mentoring the next generation of petrophysics and integrators. Bob has a long track record in integrated reservoir studies with an emphasis on seismic reservoir characterization. He also has extensive experience with workstations and computers relating to log analysis, geological mapping, and stratigraphic modeling using seismic attributes and geostatistics. Bob is a former SPWLA Distinguished Lecturer, an AAPG Certified Petroleum Geologist, past president of the SPE GCS Reservoir Study Group and a member of the SPWLA and SPE. He has published numerous papers in the SPWLA, AAPG, GCAGS and GSA on a variety of topics dealing with reservoirs of both conventional and unconventional natures. He has given a talk to SPE, SPWLA, GSA, and SEG sections all over the world.