Because of the difficulty in quantifying the areal and vertical variation of every CBM parameter, simulation can be used to test the impact of various parameter combinations on overall reservoir performance. Data-Driven Reservoir Modeling With continued production, the matrix contracts as gas desorbs from the coal, resulting in an increase in absolute permeability. Some operators use mature-well data to create a series of type curves for estimating the performance of new wells. They also can be recognized by a combination of other log responses including: Caliper logs also can be a useful coal indicator because coal intervals are often washed out by drilling operations. About Spe Reservoir Evaluation & Engineering SPE Reservoir Evaluation & Engineering covers a wide range of topics, including reservoir characterization, geology and geophysics, core analysis, well logging, well testing, reservoir management, EOR, fluid mechanics, performance prediction, and … 402 – 413, May 2020. SPE Reservoir Evaluation & Engineering covers a wide range of topics, including reservoir characterization, geology and geophysics, core analysis, well logging, well testing, reservoir management, EOR, fluid mechanics, performance prediction, and reservoir simulation. Fig. The ISSN of SPE Reservoir Evaluation and Engineering journal is 10946470. He also serves as a referee for several US and international research foundations. Conventional drillstem or buildup tests can be run in CBM wells, but, in many cases, the reservoir pressure will be too low to lift produced water to the surface. These estimates begin with qualitative values generated before drilling appraisal wells and extend to quantitative reserve numbers based on the production history of development wells. Micrologs can provide a qualitative indication of coal permeability based on the degree of separation between the micronormal and microinverse curves. For example, drillstem tests conducted in low-permeability coal seams in the Ordos basin of China were followed by injection/falloff tests that provided similar results. Reservoir Conformance Improvement News, resources, shared expertise and community connection for reservoir professionals. Larger density cutoff values are sometimes used, but this requires that a lower average gas content be used as well. Join industry experts as they explore solutions to real problems and trending topics in reservoir engineering. Yalniz, U. and Ozkan, E.: “A Generalized Friction-Factor Correlation To Compute Pressure Drop in Horizontal Wells,” SPE Production and Facilities (Nov. 2001) 232. Date: Tuesday April 13th, 2021 ... Kirby has led the publication of four SPE papers outlining the use of PTA for DFIT analysis. This value, divided by the total gas content of the core, provides an estimated recovery factor (Fig. Shahab D. Mohaghegh. Generally, coal thickness is estimated by counting those intervals with a bulk density of less than 1.75 g/cm3. 1—A sorption isotherm curve showing how a recovery factor is calculated. Articles in press are accepted and edited, peer reviewed articles that are not yet assigned to volumes/issues, but are citable using DOI. During the initial screening stage, parametric studies provide a means to relate values of key reservoir parameters generically to recovery factors. The original Monograph 1 was published in 1988 and was designed to assist industry practitioners in the application of oil & gas reserves approved by SPE and SPEE. Conventional well-test analyses generally are preferred for analyzing data from CBM well tests because they are relatively straightforward. However, if properties vary dramatically, multiple pilots may be needed. Fig. SPE Reservoir Evaluation & Engineering covers a wide range of topics, including reservoir characterization, geology and geophysics, core analysis, well logging, well testing, reservoir management, EOR, fluid mechanics, performance prediction, and reservoir simulation. However, because of their complexity, rate and reserve forecasts for CBM reservoirs are generally less certain than the forecasts for conventional oil and gas reservoirs. The number of appraisal wells that should be drilled and offset by additional wells to create pilots must be determined. 31, Issue 2-4, pp 125-133. Perhaps the most valuable use of CBM simulation is to evaluate the effects of variations in key parameters. Caliper logs also may indicate permeability by detecting a thicker mudcake across permeable coals. Well-test permeability is a critical parameter for estimating CBM production rates and ultimate recovery. The increasing gas rates that characterize early CBM reservoir behavior preclude the application of decline-curve analysis during this period. Numerical simulation can be used to determine how often shut-in pressures should be obtained, and these often can be measured in conjunction with well work or other planned shut-in periods. If the gas rates are increasing but clearly subeconomic, the pilot can be expanded at the current well spacing to a nine-spot or other configuration to minimize water influx and assess whether economic rates will be achievable. At this point, the canisters are opened, and the cores can be described. . If the permeability range is unknown, the test can be designed for the lowest acceptable permeability that would result in a viable project, usually 1 to 5 md, depending on other factors such as coal thickness, gas content, and initial saturation state. High apparent neutron and sonic porosities, Changes in the rate of drilling penetration, Quantify variations in key reservoir parameters, Assess the ability to dewater the reservoir as indicated by decreasing water rates and reservoir pressures, Determine gas productivity and the potential for commercial gas rates, The ability to integrate widely different data types, Help resolve data discrepancies and provide key insights into production mechanisms, Understand and revise the geologic model including estimates of aquifer size and strength, Provide a reasonable basis for rate and reserve estimates, Substantial production and reservoir pressure data. The data from these tests can be analyzed with conventional methods. the use of cookies. Injection/falloff tests are more expensive than slug tests and buildup tests, but they have at least three advantages. Effective permeability also may vary because of changes in absolute permeability as the reservoir is produced. This includes bitumen, shale, heavy, and viscous oil. Effective permeability will change during the productive life of a CBM reservoir because of changes in relative permeability as fluid saturations change. All rights reserved. National Petroleum Technology Office Other properties, such as compressibility and gas storage capacity, are difficult to measure in the lab and can range over several orders of magnitude. Buildup tests, injection/falloff tests, and slug tests each have been used successfully to determine critical reservoir and completion parameters in CBM reservoirs. Gas content values are obtained from coal core-desorption measurements corrected for lost gas and residual gas. Describes computer methods for setting up a numerical model and solving flow equations. An alternative to crushing the entire core is to first slab the core and crush one-half. This 1998 update maintains the general form and content of the original. Determining accurate coalbed reservoir gas-in-place parameters is often a difficult, time-consuming process, and the resulting estimates must be revised many times as additional wells are drilled and more information becomes available. Fig. SPE Live: Reservoir Sampling: Why? This method is dependent on production data and implicitly assumes decreasing gas production in its forecast. The Society of Petroleum Engineers (SPE) is a not-for-profit organization. Covers the application of a wide range of topics, including reservoir characterization, geology and geophysics, core analysis, well logging, well testing, reservoir management, enhanced oil recovery, fluid mechanics, performance prediction, reservoir simulation, digital energy, uncertainty/risk assessment, information management, resource and reserve evaluation, portfolio/asset management, project … Event hosted by Society of Petroleum Engineers International February 9, 2021 – February 9, 2021 Online event Values of several hundred scf/ton are quite common, although values can range from less than 10 to more than 1,000 scf/ton in high-rank coals. With some information about the type of hydrocarbon in the reservoir, this relation can be converted into saturation vs. height above the free water level relation. Carbon Dioxide Capture, Utilization and Storage. In some cases, however, reservoir and flow conditions do not follow the assumptions on which conventional well-test analysis methods are based. After the injection period, the well is shut in and the bottomhole pressure is monitored for a period of time that is usually approximately twice the injection time. These changes can be tracked over time with pressure-transient testing. INTERA’s Michael Hannon, PhD, Geoscientist, recently had two papers featured in the Society of Petroleum Engineers (SPE) Reservoir Evaluation & Engineering Journal. where. In addition to the usual data types required for numerical simulation, CBM simulation requires gas content values at initial reservoir conditions, sorption isotherms, the diffusion coefficient, and parameters to estimate changes in absolute permeability as a function of pore-pressure depletion and gas desorption. Tests with two-phase flow may be required to track permeability changes over the life of a field because permeability can vary significantly as a function of pressure and gas desorption as a CBM reservoir is produced. This typically is done by rapidly changing the fluid level in the well. Slug test results may be used to design other single or multiple well tests for determining additional reservoir parameters. Estimates of remaining CBM reserves are commonly made throughout the life of a project. 63: 2018: Slug tests and injection/falloff tests performed before production are most likely to result in a single-phase flow of water. Although coal has a dual porosity nature, most CBM tests can be analyzed with a homogeneous model because all the Darcy flow occurs within the cleat system. Numerical simulation should be used to optimize these values and predict the performance of the pilot on the basis of individual reservoir characteristics. Download Spe Reservoir Evaluation Engineering books, Projects Investigating Oil Recovery From Naturally Fractured Reservoirs. Mudlogging can detect coal seams through a combination of: Mudlogging is recommended especially for exploratory or appraisal wells, which may contain unexpected coal seams or other gas-bearing lithologies. Robert D. Sydansk and Laura Romero-Zeron. Cleat porosities, which are difficult to measure, typically are assigned values ranging from 0.01 to 0.05. Learn More » Multiple well tests can be used to indicate the degree of communication between wells and to determine permeability anisotropy. The uncrushed half can be preserved for additional work including petrographic examination of the core and future coal analyses. The objective of this workshop is to address reservoir monitoring and surveillance challenges, advancements of technologies, and applications that integrate different data sets of multiscale throughout reservoir life cycle. A more sophisticated tool for estimating reserves at this stage is numerical reservoir simulation, which can be used to determine whether the assumed abandonment pressure is realistic for the expected range of permeabilities. Low-Energy Processes for Unconventional Oil Recovery addresses reservoir engineering, low-energy recovery processes, and resource access challenges for abundant unconventional oil. water weight fraction, lbm water/lbm coal. 1998. If this pilot is unable to produce gas at economic rates, then it becomes unlikely that additional pilots will be successful, leading to an early exit from the project. Reservoir properties can vary rapidly, and many variations are difficult to quantify. SPE.org uses cookies to deliver the best possible experience. A typical pilot consists of several closely spaced wells that are produced for a sufficient period to understand the potential of the reservoir and determine if it can be developed commercially. PLEASE NOTE: Registration for technical events CLOSES 24-hrs PRIOR to the event, pending availability. Several references exist to guide this work including a comprehensive publication by the Gas Research Institute (GRI).[1]. It usually is easier to measure injection rates in an injection/falloff test than it is to estimate flow rates in a drillstem test when fluids are not produced to the surface. This work will ensure, for example, that a good CBM reservoir is not being abandoned because of poor well completions. A good approach is to drill the first pilot wells around the most prospective appraisal well. If a complete log suite is available, sophisticated computer models may be applied to estimate multiple coal characteristics.[3]. A downhole shut-in device is critical in underpressured reservoirs to avoid problems of falling liquid levels in the wellbore during the falloff period. However, slug tests can be used only in underpressured reservoirs and may not investigate a large reservoir volume. The maximum acceptable injection pressure should be less than 80% of the estimated parting pressure. Coals typically demonstrate greater permeability in the face cleat direction because these fractures are more continuous and have wider apertures than butt cleats. Decline-curve analysis can be used in the mid-to-late stages of the field’s producing life. SPE Reservoir Evaluation & Engineering Journal, Formation Evaluation 23 (2): 772 – 782. With this model, we can predict, for a given rock type, the hydrocarbon saturation at any elevation in the reservoir and compare it with that computed from the Archie method. DOI: 10.2118/200499-PA. Tandon, S. and Heidari, Z., 2019. Use this section to list papers in OnePetro that a reader who wants to learn more should definitely read, Use this section to provide links to relevant material on websites other than PetroWiki and OnePetro, https://petrowiki.spe.org/index.php?title=CBM_reservoir_evaluation&oldid=51607, Copyright 2012-2021, Society of Petroleum Engineers. A pattern containing an isolated center well, such as a five-spot, is preferable and can be implemented with a successful appraisal well as part of the pattern. Slug tests are relatively simple to run and are inexpensive compared with other types of well tests. Core analyses are a critical part of analyzing CBM reservoirs to determine gas saturations. It is important to understand both the direction and magnitude of permeability anisotropy early in the project life because it can have a significant impact on the choice of well-pattern geometry and orientation and well spacing.