Hom B. Chetri

Integration of Dynamic data of pilot Waterflood with Rock Fabric - Implications for the Full Field Waterflood Startup in Mauddud reservoir, North Kuwait

The Mauddud limestone of Early Cretaceous is multi-billion barrel depletion drive reservoir undergoing re-development with a planned 260,000 BWPD seawater injection. Injection-production history and dynamic data integration with a static reservoir description of the two waterflood pilots illustrates much of what can be expected in the larger scale waterflood. Detail cross-sections were build incorporating geological, petrophysical, surveillance and production data to understand reservoir performance under water flood. . Geocellular models based on 3-D seismic and detail core sedementology was constructed and simulation was done to facilitate this understanding. Over the two and half years of Pilot life great variety of data were acquired which includes: extensive open hole logs including CMR/NMR, FMI and RFT, Conventional and preserved cores, core sedimentological and fracture study, Geochemical (latroscan & Residual Salt Analysis) analysis, Geomechanical & Reservoir stress analysis, interference testing, production and injection profile logs, time lapse pulse neutron logs, static bottom hole pressures and pressure build up surveys. Synergistic integration and interpretation of multidisciplinary pilot wells data, has given a detail insight of the controls of fluid flow in the reservoir and the understanding was carried forward to the full field development of Mauddud reservoir using 1-9 spot pattern flooding. The major controls on the pilot water movements are; 1) Facies variation and thief zones, 2) Injector conformance 3)regional reservoir pressure gradients around the pilots. The pilots have proven the pressure connectivity on the larger scale (250 acre inverted 9 spot) through surveillance gathered outside the pilot patterns. This adds confidence to the predictions of flood performance success across the development area and confirms that the planned pattern flood is appropriate. Mechanism of water breakthrough was studied and potential sweep efficiencies in the relatively lower permeability facies were analyzed through production and pulsed-neutron logging and by in-fill drilling. The three vertical hydraulic units identified by field RFT data were confirmed by vertical sweep profile. The more depleted upper zone is the target of the existing pilots. These characteristics are expected in the larger scale waterflood and perforation strategy is designed to optimize conformance between injector and producer and to minimize early injection breakthroughs and maximize vertical and areal sweep efficiency. The observed time to water breakthrough, observed vertical and aerial sweep, and the controlling geologic description has been used to refine reservoir simulators allowing them to more accurately predict production and more importantly water-cut profiles and recovery factors for this important re-development.

Waterflood Optimization and its impact using Intelligent Digital Oil Field (iDOF) Smart Workflow Processes: A Pilot Study in Sabriyah Mauddud, North Kuwait

erms. The transformation of raw data into information is achieved through intelligent, automated work processes, which are referred to in this paper as “smart workflows.” These smart workflows assist engineers with daily well surveillance activities, aid productivity, and help improve the speed and quality of their decision-making process. The workflow presented is related to waterflood management; however, it is part of a family of smart workflows (e.g., electrical submersible pump [ESP], subsurface waterflood optimization [SWFO], and smart production surveillance [SPS] workflows), which have been discussed in other work. These smart workflows and a commercial software, Oil Field Manager (OFM) for Decline Curve Analysis (DCA), have also been used in waterflood optimization for the optimum production allowable selection, with the ultimate goal of improving asset performance. This paper shares how these smart workflows are used for waterflood optimization and illustrates a case study of an injection pattern optimization and its impact on production. Comprehensive monitoring of the waterflood has been performed using real-time data through iDOF smart workflow processes, illustrating the analysis of real-time data, which includes pump intake pressure, flowline pressure, water cut (WC), and flowing bottomhole pressures. Other data used include static bottomhole pressure, production log results, and production flow tests. Monitoring is planned in such a way to understand waterflood movement within the reservoir from injector to producers and its impact on the production behavior of the surrounding producers. A positive response in terms of pressure maintenance and production increase has been observed and confirmed using various analytical tools.

Integrated Reservoir Management Utilising a Portfolio Approach to Beat the Impact of Delayed Water Injection Projects - Opportunistic Strategic Alignment in North Kuwait

North Kuwait is blessed with multiple reservoirs stacked, Tuba at the shallowest and Ratawi at the deepest level. Water flood expansion was the key ingredient to provide the short term production assurance for the Asset. Field development activities have been progressing for two of the major stacked reservoirs with lion’s share of incremental production (Mauddud & Upper Burgan), assuming that these reservoirs will get the benefit of water injection, to cope up with the enhanced level of production. Unfortunately, the water injection projects have been delayed till the end of 2013, leading to rapid decline in reservoir pressures and erosion in the well performance of the producers (naturally flowing as well as on artificial lift). A comprehensive review of the portfolio of all reservoirs was made vis-a-vis the drilling/ workover activities. Complete history of pressure-production data for last 40 years was analyzed using OFM. The output from the reservoir simulation models was analyzed & discussed with multi-disciplinary teams. Aggressive surveillance & data integration plan was made and implemented to identify the focus areas, from where “new” production can be accelerated and / or controlled, adhering to the best reservoir management practice. Isochronal reservoir pressure maps were updated with full field static bottom hole pressure surveys. Detailed analysis of the RFT/ PLT data was performed to optimize the perforations at layers with high reservoir pressure. New wells from shallower reservoirs were deepened to the reservoirs enjoying the active water drive and accordingly, completed for short term production till the water injection expansion project is commissioned. Integrated reservoir management approach was followed throughout the gamut of field development activities with multi-skill expertize reviewing as peers for smart decisions. The paper’s objective is to share the integrated Reservoir management approach to beat the impact of delayed water injection projects on overall production portfolio, without compromising the technical requirement of voidage replacement ratio for depletion drive reservoirs with best practices approach.

Doubling the Production from a Mature Reservoir in North Kuwait-Challenges, Achievements & Lessons Learnt

Sabiriyah Lower Burgan is a clastic reservoir in North Kuwait on continuous production for the last 45 years. The reservoir, on active water drive, has its inherent problem of rapid increase in water cut, the production performance of wells declining drastically after water cut l evel of 40%. Many wells became idle in th e past, with overall well efficiency (ratio of flowing to total number of wells) of 60%. The formal strategy for production had been focused on “keeping the active perforations away from water”. Attempts were made in the past neither to install any artificial lift nor to have a campaign for water shut off/new technology applications.

Integrated approach to infer fractures and manage the waterflood projects in mauddud reservoir, Raudhatain & Sabiriyah fields, north Kuwait

Mauddud limestones are multi-billion barrel depletion drive reservoirs undergoing massive development efforts with a planned 700% increase in oil production through pattern waterflood. The conceptual development plan for the reservoir, in view of uncertainty about the degree of fracturing and its resultant impact , has been kept flexible allowing for a change in development strategy, if deemed necessary. A review of the performance of historical offtake points and data acquired so far illustrates a large variation in static and dynamic behavior areally as well as vertically. Integration of multi-source evidences to describe the anomalies and infer the probable existence of fractures is done to predict the impact on the inverted 9-spot waterflood patterns likely to be operative next year. The integrated approach illustrates the significance of fluid & rock data, Pressure-Production data and information obtained from new & old logs to revisit the reservoir description for inferring fractures. Recently acquired 3-D seismic data exhibited faults of various magnitudes scattered over the major area of historical offtake. The spread of cumulative production, well PI and Qmax areally revealed a linkage between the faulted & non-faulted area. A review of past PBU data coupled with core data further indicated the existence of fractures. A review of resistivity and caliper response in old logs and interpretation of image logs also deciphered the presence of fractures. Scanning through the drilling and completion histories of wells was done to authenticate the inferred fractures in Mauddud reservoir. The performance of the two waterflood pilots in operation was also reviewed to see areal and vertical connectivity utilizing the Pressure-production and RFT/PLT data to infer any flow through the fracture system. Preliminary studies indicate that 7 inverted nine spot patterns ( one-fourth of the total number of patterns) are likely to be impacted, by the fractures due to premature breakthrough of water injected and reduction in the sweep efficiency. Analytical methods indicate the loss in recovery to the extent of 12 to 18% if significant fractures are present within the patterns. However, in case of minor degree of fracturing, Injectivities and sweep efficiency may improve. In light of uncertainties on extent of fracturing, future work plan includes review of core, Image logs & productivity/Injectivity data from new wells and Pressure Build up data gathering with bottom hole shutting- in in key wells. The integrated approach has helped to understand the flow dynamics of injected water better and recommendations leading to better management of the water injection project for Mauddud reservoir.