Wells in a field offshore South East Sumatra, Indonesia, produce oil at very high rates and water cut. Under these conditions the reservoir is susceptible to fines migration with the associated pore plugging and production decline. Conventional acid treatments to dissolve fines in the near well bore have been effective for limited periods. However after some days or weeks of production, rates have been observed to fall as fines once again migrate, accumulate and plug the formation and gravel pack. Retarded mud acid formulations -that claim fines stabilization- have also been put into practice in an attempt to solve the problem. These formulations have also been ineffective and fines migration remained an unsolved problem. A novel technique to inhibit fines migration through the "Surface Adsorption Polymerization" technique has been used to stabilize the fines around the borehole. The technique is a three-stage process that results in fines being coated with a solid thin polymer film that is stable at high flow (shear) rate locking the fines in place. The validity of the approach has been confirmed with flow tests in cores from the field under study, and has been validated by field results. This paper presents the process followed to implement this technique in the field, case histories and production data of the treated wells. Introduction Formation fines, in general comprised of aluminosilicate particles a few microns in diameter, are found in the majority of oil and gas producing sandstones. Fines become a problem when they swell or detach from the pore wall and migrate through rock matrix with produced fluids. These mobile fines eventually clog in pore throats, plugging the pores and causing a reduction of rock permeability. Factors contributing to the production of fines include exposure to high pH fluids, exposure to fresh (low salinity) water, wettability and high fluid velocity1,2. Quaternary ammonium salts, sulfonated polymers, hydrolyzable metal ions and organosilane products have been used to mitigate fines migration. These chemicals are adsorbed on the rock surface and prevent detachment of fines by forming a protective shield around negatively charged clay particles. These additives have often been termed permanent clay stabilizers, and when compared to inorganic salt stabilizers such as KCl or NH4Cl, they can provide longer-term protection. The fact is that these stabilizers are far from being permanent since they still rely on charge neutralization. The limitations of these treatments are:Charge neutralization does not prevent mechanical dislodgment of particles subjected to high fluid velocity3.Fines with low charge density (feldspars) are not controlled effectively by charge neutralization.Only temporary control is obtained because the polyvalent ions tend to desorb over time as large volumes of fluid are produced. Points 1) and 3) are particularly true in the field of the study, where producing rates of 10,000 to 30,000 BFPD at 90–98% water cut promote mechanical dislodgment of particles and ion desorption.
TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractIn mature, multi layered reservoirs with commingled, dual string, and gravel packed completions, selecting reliable acid stimulation candidates has always been a challenge. Achieving a high success ratio under these conditions requires a riskbased selection process, supported by reservoir understanding and characterization.As the traditional workflow, acid stimulation candidate selection starts with a thorough production performance review. Production history is provided on a string-by-string basis, and nodal analysis modeled based on production performance. Perforation and completions are evaluated to identify any damage. Logs are then reviewed to evaluate mineralogy and petrophysics. In this workflow, candidate selection is refined by reservoir modeling to predict the production gain in field level and production decline prediction. A decision and risk analysis is conducted with a strong emphasis on range of probability evaluates all possible outcomes associated with success and failure ratio. An economic analysis is evaluated based on risk analysis. This workflow is developed and tested in Bokor field, off the coast of Sarawak, Malaysia.After acid stimulation campaigns spanning over 6 reservoirs, the results have yielded to 40% oil production gain. Six strings showed an increment in oil rate, a reduction in water cut and an increase in productivity. Overall, the fine tuned acid job design combined with visco-elastic surfactant diversion technique proved to be effective. This paper presents the comprehensive workflow developed and implemented by the Bokor Project Management Team (BPMT) encompassing all the components necessary to deliver a risk based decision and therefore the optimum results.
Brownfields are often characterized by a varying degree of maturity, both within the field and within individual reservoir units. This variation makes infill drilling more prospective in areas with fewer well penetrations and completions and less production. However, these areas are inherently more uncertain, with geological, petrophysical, and structural parameters particularly affected. A novel workflow solves the complex problem of uncertainty assessment and risk management in a brownfield redevelopment. Traditionally, a single deterministic reservoir model is built, matched, and used for predictions and infill planning. The availability of sophisticated simulation workflow tools enable the team now to explore the practical aspects of performing sophisticated reservoir description, static model construction, history matching, and forecast uncertainty analysis. Incorporated into multiple equiprobable reservoir descriptions, uncertainties are carried from the static model construction throughout the entire dynamic modeling process. History matching is conducted for all realizations, and the match quality is assessed by means of statistical analysis. The workflow facilitates generating hydrocarbon thickness maps by using the average column thickness of many simulation models instead of a dedicated single one. Target selection also accounts for possible sweep and sand risks by means of maps showing the standard deviation of the column thickness. The new framework is applied to a conceptual redevelopment of a brownfield. It increases the understanding of fluid flow processes in the reservoirs and is a vital component of the decision and risk analysis for the concept selection stage.
The Reserve Technical Potential Management System (RTPMS) is divided into 5 main stages and associated together with the Petroleum Reserve Management System by SPE. The main aim by merging these two concepts is to improve understanding of the reserves pool and therefore provide a practical guideline on a standard definition for high level planning and day-to-day operations. The concept is being developed with major focus on the rehabilitation of mature fields where each barrel of oil counts and uncertainty, both technical and economical, are becoming more challenging at industry level. High decline in productivity and increased operational challenges are common issues for mature fields. Recurrently, lower recovery factors are mainly driven by reservoir characterization uncertainty and management, geological complexity, limited resources and operational efficiency. This paper addresses some of these challenges in an integrated manner. Each stage is mapped and associated with the SPE Petroleum Reserve Management System, the project management control level, the time cycle (short: operation efficiency, medium : production optimization and long: reservoir management), a digital oilfield concept, the roles and responsibilities of the stakeholders, the technology groups and their key technologies. The five stages are defined as; 1) Actual Potential, 2) Operational Technical Potential, 3) Constrained Technical Potential, 4) Theoretical Technical Potential and 5) Ultimate Technical Potential. The concept has been developed based on lessons learnt and best practices acquired in mature field rehabilitation projects.
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