|Theme||Visible||Selectable||Appearance||Zoom Range (now: 0)|
In the Court field, the middle Bakken Sand Pool has been operated as a heavy oil waterflood for over 15 years. However, unrecovered oil volumes in the pool remain attractive for improved recovery schemes.
Recently, the Court middle Bakken reservoir model was updated to evaluate the potential for downspacing and waterflood optimization of the reservoir. The potential for 20 acre downspacing for both infill drilling and additional water injection was identified by this study.
As part of the additional development program, an injectorproducer well pair was drilled to create a new injection pattern with reduced inter-well spacing. Reservoir pressures, water saturation and effective permeability to water in the pattern were determined by RFT and log data. Pattern characterization was complemented by an interference test, including all the wells in the pattern. Analytical and numerical tools were used in the test design. The most comprehensive results were obtained by local grid refinement of the pattern area in the full field simulation model. Unavoidable interference with a neighboring pattern during the test was predicted. In order to account for this effect, it was decided to run the test with the new injector active intermittently.
The complete test design and analysis of the results are described. In addition, a comparison of pressure measurements by downhole gauge and acoustic well sounder are presented.
Ambastha, Anil Kumar (Chevron/KOC) | Dashti, Qasem M. (Kuwait Oil Company) | Maizeret, Pierre-David (Schlumberger Vietnam Services) | Al-Farhan, Farhan (Schlumberger) | Bou-Mikael, Sami (Chevron Corp.) | Rajan, Sasi (Kuwait Oil Company)
Abstract The Wara reservoir has been producing for over 60 years and its pressure has slowly decreased over the years, now below saturation pressure in some structurally-high areas where gas cap has increased in size compared to very small initial gas caps in these areas. A peripheral, water injection project is being considered to maintain the pressure above bubble point and improve oil recovery from the flank areas. However, limited information is available concerning Wara reservoir heterogeneity. Shut-in of all Wara producers provided an "once-in-a-lifetime" opportunity to carry out a fieldwide pressure data acquisition campaign. Over a period of six months (Nov. 2006-May 2007), 127 static bottom-hole pressure (SBHP) surveys, 26 pressure buildup (PBU) tests (including buildup tests for 2 active wells of the interference test program) and 3 interference tests were conducted. Each interference test involved one active well and 3–6 observation wells. This paper describes a systematic methodology to select wells to test on a fieldwide basis, test design exercise, data acquisition program execution, and observations and conclusions reached from this data set. Over the duration of the campaign, an increasing pressure trend was observed in almost all wells slated for PBU and interference tests. This observation was made possible due to multiple SBHP recordings in these wells. The linearly-increasing pressure trend had to be taken into account in the analyses of the buildup tests to avoid interpreting wrong boundary conditions. Wellbore dynamics also initially affected some pressure buildup tests and were later circumvented by the use of a downhole shut-in tool (DHST) to limit the phase segregation effect. The transient analyses revealed different flow regimes, from infinite-acting radial flow, to dual-layer and radial composite with or without sealing faults. From the SBHP data, maps have been made to assist in identifying compartments. One interference test showed anisotropy which could be critical in the implementation of a water injection project. Overall, the interpretation of the data from this extensive data acquisition campaign has shed light on reservoir heterogeneities that have been integrated with changes made in a fullfield, "Wara only", history-matched simulation model. Background and Study Objectives The Wara reservoir is the uppermost, sandstone interval of the Greater Burgan field and is separated from the Burgan sands (Third Sand Upper, Third Sand Middle, Third Sand Lower, and Fourth Sand) by tight, limestone Mauddud reservoir. Any fluid communication between the Wara and Burgan sands has to occur through partially-sealing faults with throws considerably larger than the Mauddud thickness. In the past, SBHP and pressure transient data have been acquired at some wells completed in Wara on a non-routine basis.
Abstract The topic of inter-well communication in unconventional reservoirs has received significant attention as it has direct implications to well spacing considerations. However, it has been the observation of the authors that interference is often inferred without direct evidence of its occurrence, or without an understanding of the various mechanisms of interference. This paper presents a rigorous procedure for correctly identifying interference during a well's production cycle. First, the various mechanisms of interference are defined. Next, analytical simulations are run to reveal the expected behavior for interference through fractures and reservoir matrix. Data validation is performed, followed by a procedure for identifying interference. Finally, the data is history matched with numerical models based on the learning from the previous step. The approach is applied to an eight well pad in the Horn River Basin. Two wells were found to be in communication. From this procedure, it was possible to determine that these wells are in communication through fractures or high permeability channels. The procedure in this paper is designed to help production analysts diagnose interference and avoid common pitfalls. The workflow is generalized and can be applied to other multi-well pad completions.
Abstract Tamar is a high permeability clastic gas reservoir that behaves like a well-connected tank, in many respects. At the same time, it has a significant level of complexity. The reservoir is comprised of three sand intervals, which are separated vertically by shales and broken into a number of fault blocks. While the degree of aquifer support has been an uncertainty, it is believed that the field demonstrates components of both bottom water and edge water drive. All Tamar wells were equipped with permanent downhole pressure and temperature gauges, and the surveillance of these pressure and rate data over the five-year production history has provided an unusually comprehensive data set. This dataset supports the high-resolution evaluation of well interferences and multi-well analysis. Investigation of the data on a well-by-well basis using conventional Pressure Transient Analysis techniques provided valuable insights, albeit primarily at the fault block scale. However, extending these investigations to the field scale generated some conflicting interpretations which could not be resolved by traditional PTA and standard reservoir engineering techniques.
Abstract Well spacing and completion optimization in tight and shale reservoirs is a multi-dimensional task which comprise reservoir rock and fluid characterization, well performance study, inter-well communication analysis, and economic evaluation. Two sources of pressure data for characterization of inter-well communication include offset well pressure monitoring during hydraulic fracturing and controlled communication (interference) tests through staggered production. Both types of inter-well communication tests have become common among the operators in tight and shale reservoirs. However, quantitative analysis tools for interpretation of the test results are in their infancy. The focus of this study is quantitative analysis of pressure interference tests. In this study, an analytical model is developed for quantitative analysis of communication between multi-fractured horizontal wells (MFHWs) using pressure data from production and monitoring well pairs. The governing partial differential equation for the more general case of coupled flow in hydraulic fracture and matrix systems is solved using the Laplace transform. In order to validate the analytical model, the results from the analytical solution are compared against numerical simulation models. The analytical model of this study is applied to two field case from Montney formation. In these cases, a well from a multi-well pad is put on production and bottom-hole pressure of a monitoring well from the same pad is recorded using down-hole recorders. Communications between the wells is quantified using the analytical models of this study. The model of this study serves as a novel and practical tool for quantitative analysis and interpretation of inter-well communication in MFHWs. Integration of the model with other direct diagnostic and measurement tools can provide insight into optimized completion intensity for MFHWs.