Microseismic monitoring has become the approach most often employed to gain an in-situ understanding of the rock’s response during hydraulic fracture stimulations. The utilization of distributed geophone arrays around treatments has provided an opportunity to investigate the way these fractures develop by examining the microseismic events recorded during a stimulation. Through microseismic (MS) monitoring currently being carried out in the Horn River formation, geophysicists and reservoir engineers have incorporated MS field data and its original interpretation to constrain and validate reservoir models. Generally, we have observed that overall fracture height, width and length, orientation, and growth vary from formation to formation and within each formation.
In the presence of uncertainty in reservoir models input data required for determining the best estimate of a value, probabilistic methods are used. Risk analysis is a technique to quantify the impact of uncertainties on output variables, and to determine a range of possible outcomes, as opposed to a single deterministic solution. The uncertainty in the output also provides a measure of the validity of a reservoir model. In this presentation we apply Monte Carlo simulation using Latin Hypercube sampling. Probability density functions (PDFs) and cumulative distribution functions (CDFs) that describe the likely values of MS fracture half-length and MS fracture height are used as input parameters into the reservoir model. PDFs and CDFs are established and used to provide more realistic estimates of stimulation parameters such as Stimulated Reservoir Volume (SRV) which are subsequently calibrated with MS SRVs.
The interpretation of MS events provides an upper bound value for stage fracture half-length and fracture height in unconventional shale gas reservoirs. The cumulative distribution function of stage fracture half-length and fracture height on a well basis on a multi-fractured horizontal well pad provides insight of what the ultimate stage by stage SRV could be after pressure depletion occurs, and provides guidance for well spacing and well placement in multiwell pad design. This allows a probabilistic approach to production forecasting and reserves estimation and provides a robust P10 estimate of Expected Ultimate Recovery and the Recovery Factor. This approach differs from previous work that is based on strong collaborative work between geophysicists and reservoir engineers.
This presentation features a recent multi-well pad stimulation and MS interpretation. Constrained Analytical Models are used as a ‘quick look’ first pass into numerical simulation. The result is production forecasting for different reserves categories including Proved Developed Producing (PDP), Proved and Probable Developed Producing (PPDP) and Undeveloped (PUD & PPUD). Furthermore, some of the design considerations of the newly completed multi-well pad, surveillance data such as production logs, chemical fluid and radioactive tracers and production indications will be addressed and considered, concluding with a discussion of the results.
About the Author(s)
Claudio Virues is a Senior Reservoir Engineer at Nexen Energy ULC a wholly-owned subsidiary of CNOOC. Previously he worked for Encana Corporation as reservoir, production and reserves engineer in the tight shallow gas vertical well Infill Development Project in Suffield area, tight gas horizontal well Infill Development Project in the Carbonate Jean Marie Play and in the Appraisal and Exploration Team for the Duvernay and Montney Plays in the Alberta, British Columbia and in the Deep Basin in Canada respectively. His research interests include flowback and interference analysis, hydraulic fracturing modeling and geomechanics, value integration of geophysics and engineering, rate and pressure transient analysis, production forecast and reserves estimation.
Claudio has authored and/or coauthored more than 25 papers in the last 4 years. He holds a B.Sc. in Naval Engineering and Marine Architecture from Buenos Aires Technological University, a M.Sc. in Reservoir Engineering from Buenos Aires Institute of Technology (B.A.I.T.) and a M.Eng. in Chemical and Petroleum Engineering with Honors from the University of Calgary.
Claudio is a member of the SPE where he is a Canada Region member of Events and Training committees, a Calgary Section Chairman-Elect; a member of the SPEE where he is part of the Membership commitee; and member of CSPG, CSEG, AAPG, CWLS, and SPWLA. He is a recipient of the 2015 SPE Calgary Section Innovative Section Growth Award.