Conference Paper

Design of an Economical Polymer Flood Pilot Addressing Field Development Uncertainties in the Sabriyah Upper Burgan Reservoir of North Kuwait

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The Sabriyah Upper Burgan is a major oil reservoir in North Kuwait with high oil saturation and is currently considered for mobility control via polymer flooding. Although there is high confidence in the selected technology, there are technological and geologic challenges that must be understood to transition towards phased commercial field development. Engineering and geologic screening suggested that chemical flood technologies were superior to either miscible gas or waterflood technologies. Of the chemical flood technologies, mobility control flooding was considered the best choice due to available water ion composition and total dissolved solids (TDS). Evaluation of operational and economic considerations were instrumental in recommending mobility control polymer flooding for pilot testing. Laboratory selected acceptable polymer for use with coreflood incremental oil recovery being up to 9% OOIP. Numerical simulation recommended two commercial size pilots, a 3-pattern and a 5-pattern of irregular five spots, with forecast incremental oil recovery factors of 5.6% OOIP over waterflood. Geologic uncertainty is the greatest challenge in the oil and gas industry, which is exacerbated with any EOR project. Screening of the Upper Burgan reservoirs indicates that UB4 channel sands are the best candidates for EOR technologies. Reservoir quality is excellent and there is sufficient reservoir volume in the northwest quadrant of the field to justify not only a pilot but also future expansion. There is a limited edge water drive of unknown strength that will need to be assessed. The channel facies sandstones have porosities of +25%, permeabilities in the Darcy range, and initial oil saturations of +90%. Pore volume (PV) of the two recommended pilot varies from 29 to 45 million barrels. A total of 0.7 PV of polymer is expected to be injected in 5.6 and 7.9 years for the 3-pattern pilot and the 5-pattern pilot, respectively, with a water drive flush to follow for an additional 5 to 7 years. Incremental cost per incremental barrel of oil of a mobility control polymer flood which includes OPEX and CAPEX costs is $20 (USD). This paper evaluates the (commercial size) pilot design and addresses field development uncertainties.

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Conference Paper
EOR is a key focus area for sustaining long term production and maximizing of recovery in Raudhatain and Sabriyah oil fields of North Kuwait (NK). NK oil fields consist of multiple stacked reservoirs containing both clastic and carbonate with challenging temperature and formation water salinity conditions for Chemical EOR. In addition to these harsh conditions, reservoirs have geological structural complexity, reservoir heterogeneity and aquifer strength settings. Kuwait Oil Company is putting large efforts into Chemical EOR (cEOR) maturation through two ongoing ASP pilots and polymer flooding maturation studies. Ongoing studies and preliminary piloting performance results revealed that different reservoir segments have different cEOR requirements for viable incremental oil opportunities on top of ongoing water flooding. An expansion strategy has been developed that provides a view on how to transition from pilot results to larger scale commercial implementation of cEOR for each reservoir segment. This includes front end elements, beyond conventional cEOR screening studies, injectivity, conformance control, inorganic scaling, facility impact and pattern configurations. For larger scale, many additional aspects such as water source, well location, phasing, logistics and impact of back production are important factors. For commerciality, there needs to be abalance between schedule, maximizing economic recovery, operability,availability of source water and costs. A holistic, structured approach has been established in defining production forecasts and life cycle cost estimates for ASP, SP and polymer development concepts screening for major NK reservoirs. The approach has allowed comparison between recovery methods and reservoirs which helped in defining an EOR expansion plan. The novelty in this EOR expansion strategy is in application of a structured and holistic approach to map viable cEOR technologies to different reservoir segments based on in-depth screening criteria. The methodology allowed generating "standardized" time bound forecasts and cost estimates for screening a range of viable mapped cEOR methods for a range of reservoir segments- facilitating like for like comparison.
Conference Paper
With a resurgence of chemical EOR opportunities throughout the world, high concentration surfactant design has re-emerged its uneconomic face. High concentration surfactant formulation is the micellar polymer design from the past that produced high oil recoveries in the lab but were uneconomic in the field. Formulation designs must consider factors beyond simply oil recovery for economic success and to minimize production issues in the field. Analysis and comparison of micellar polymer design projects from the 1970-1980s to current SP/ASP formulation designs are discussed. A simple formulation cost calculator is showcased, costs of all formulations are presented, and price per incremental barrel produced (chemical cost only) are shown assuming a 0.1 PV of incremental recovery. Analysis concludes the following: Micellar polymer floods were phased out because they were uneconomic. Key reasons are high cost of surfactant and emulsion problems faced when produced surfactant concentration exceed a certain threshold resulting in either greater production cost or disposal of produced oil in the form an unbreakable emulsion. Alkali can improve economics as a low-cost commodity product that can be used to reduce surfactant concentration required to attain high oil recoveries. Alkali is an order of magnitude lower cost per pound than the typical surfactant and can be used as an enhancing agent to improve the performance of other injected chemicals. Alkali is not a "silver bullet" that will save economics, and adds challenges and cost for water softening, which can be economically detrimental to field projects. Many high concentration surfactant formulation floods are being re-introduced to the industry. Not only are these designs un-economic but include multiple chemicals that add complexity and cost to the facilities and difficulty for facility personnel. A formulation that requires more than $20 of chemical per barrel of incremental oil is unlikely to be economic with $50/bbl oil. Key differences between laboratory results and field implementation results are discussed. Geologic uncertainty is addressed since it is the greatest challenge to field economic success. The industry is taking steps back to an uneconomic time of chemical EOR by obscuring the difference between designs meant to increase reserves (economic oil) versus those that serve an academic or research purpose. Operators are unwittingly paying the price to advance the science of chemical EOR when service companies provide formulations that are not economic. This paper is meant to remind the industry that high concentration surfactant formulations never were economic and certainly will not be economic in today's price environment.
Conference Paper
Abstract The late Albian to early Cenomanian Burgan and Wara formations from Southeast Kuwait constitutes the largest siliciclastic oil reservoir on earth. The sedimentology and stratigraphy of Greater Burgan Field is reviewed here in terms of depositional environment and relation to global eustatic changes. An updated reservoir model has been built on a sequence stratigraphic framework from 980 wells, backed by sedimentological analyses, chemostratigraphy and biostratigraphy. The Burgan, Mauddud and Wara formations are represented by four 3rd order cycles in a coastal regime, with the lowermost cycle and the overlying rising hemicycle representing the Burgan Formation. The lowermost cycle, comprised of stacked braided channels, passes upward to tidal channel sandstones and heteroliths. Eventually a wave ravinement surface leading to a maximum flooding surface is recorded in tidal/bay to offshore environment. The regressive part of the cycle is composed of tidal channels and bars. The top of the second cycle, manifest as a grainstone-dominated carbonate platform, represents the Mauddud Formation, with the top karstified owing to late Albian/Cenomanian sea level drop. The third cycle is represented by homogenous compact offshore shales of Wara Formation overlain by the coarse fluvio-tidal siliciclastic deposition representing the regressive stage of this 3rd order cycle.
Screening criteria have been proposed for all enhanced oil recovery (EOR) methods. Data from EOR projects around the world have been examined and the optimum reservoir/oil characteristics for successful projects have been noted. The oil gravity ranges of the oils of current EOR methods have been compiled and the results are presented graphically. The proposed screening criteria are based on both field results and oil recovery mechanisms. The current state of the art for all methods is presented briefly, and relationships between them are described. Steamflooding is still the dominant EOR method. All chemical flooding has been declining, but polymers and gels are being used successfully for sweep improvement and water shutoff. Only CO2 flooding activity has increased continuously.
Screening criteria are useful for cursory examination of many candidate reservoirs before expensive reservoir descriptions and economic evaluations are done. We have used our CO2 screening criteria to estimate the total quantity of CO2 that might be needed for the oil reservoirs of the world. If only depth and oil gravity are considered, it appears that about 80% of the world's reservoirs could qualify for some type of CO2 injection. Because the decisions on future EOR projects are based more on economics than on screening criteria, future oil prices are important. Therefore, we examined the impact of oil prices on EOR activities by comparing the actual EOR oil production to that predicted by earlier Natl. Petroleum Council (NPC) reports. Although the lower prices since 1986 have reduced the number of EOR projects, the actual incremental production has been very close to that predicted for U.S. $20/bbl in the 1984 NPC report. Incremental oil production from CO2 flooding continues to increase, and now actually exceeds the predictions made for U.S. $20 oil in the NPC report, even though oil prices have been at approximately that level for some time.
Reservoir Architecture of the Cretaceous Upper Burgan Deltaic Deposits in North Kuwait. Poster Presented at the AAPG Siliclastic Reservoirs of the Middle EastGTW
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  • L Abou-Qammaz
  • R Ramalingam
  • B Kostic
  • N Connolly
  • D Meadows
Recommended Practices for Evaluation of Polymer Used in Enhanced Oil Recovery Operations
  • American Petroleum Institute