Issues and associated mitigation measures for Carbon Capture and Storage (CCS) relating to capacity, injectivity and integrity of the storage site are not trivial. Modeling of CO2 injection along wellbores is still in its infancy compared with traditional hydrocarbon modeling. While a significant amount of work has been done with respect to modeling discrete components of the storage site and associated infrastructure, validation of our modeling tools and the results still remains uncertain, particularly with respect to two phase flow in the wellbore. This paper presents a workflow for injection of CO2 into highly depleted gas fields, addressing the issues around injection modeling and the impact on surface facilities, well design and the near wellbore interface. These include: obtaining accurate predictions of phase behavior, density, and viscosity, determining the impact of delivery pressure and temperature versus reservoir conditions. Wellbore design issues such as sizing and load resistance of tubulars and metallurgy selection in order to ensure both injection performance and integrity must also be considered. Modeling CO2 in the reservoir is also discussed considering the near wellbore effects (cooling and potential ice / hydrate formation). Finally, short and long term monitoring issues are identified and the benefits and limitations of the various monitoring options are discussed.

The Kinabalu oilfield is currently producing 14,000 bopd from a peak of 40,000 bopd in 1998. Present field rejuvenation plans include drilling and completing new infill and development wells from both an existing and a new platform. Most platform wells are currently producing sand and none have been completed with sand control. Sand production has caused erosion issues and lost production due to the need for regular separator clean outs, and is a key risk factor for both existing well integrity and new well completion design. A multi-disciplinary team was tasked with determining the causes of sand production, and to develop a fit for purpose sand management strategy for this mature, brownfield redevelopment. A coupled geomechanical/sand failure model was employed to assess sand failure, and to evaluate alternatives to sand exclusion completions. The model was calibrated using existing well sand production data, then run for the proposed new wells to assess the potential for sand production over the remaining field life. The model confirmed that sand production is closely linked to reservoir depth, completion type, well inclination and, most importantly, depletion level. An objective screening process was developed to rank sand control options. This considers existing and proposed well completion architecture, facilities design/limitations, and recognises inherent data uncertainties. The systematic sand management methodology allows a consistent, objective and transparent view of benefits and risks across the different system aspects. Key selection criteria were utilised rather than arbitrary decisions based on limited and often unaudited data. The process ensured a best practice, fit for purpose, and structured sand management solution. In light of the currently low levels of sand production and the challenges associated with remedial or retro-fitting sand control, optimised surface sand management will continue to be the preferred solution for all existing wells. Predicted sand production in most new wells is manageable. Some wells targeting shallower or weaker sands would normally be sand control candidates, but re-thinking the completion design, optimising surface sand management procedures, managing drawdown and BHFP levels, and taking advantage of favourable stress vectors through oriented perforation can extend the sand free well operating envelopes over life of well production and depletion conditions, reducing or deferring the need for sand control in all but the highest sanding risk reservoirs.

The methodology for predicting sand production is in general constant across the industry. That is the determination of formation strength and field stresses and the application of them to a failure model. However, the variety of models available and their applicability and accuracy can be confusing with the results not always representing what is experienced under production conditions. This paper introduces a more holistic approach to sand production prediction which not only utilises numerical analysis, but also includes a qualitative approach using geological information. With respect to the numerical analysis the determination of various parameters used in modelling sand production and their effectiveness for different reservoir and production conditions is discussed. An overview of the various tests considered useful in calibrating these parameters is also presented. The geological approach discusses the impact of mineralogical, depositional, structural and diagenetic factors which can impact on the propensity for sand, but which are not fully taken into account by a purely numerical approach. The advantages and disadvantages of each of these aspects are presented and synergies identified between numerical and qualitative analysis. Case histories are presented which show that each of these methodologies, when used independently, can present dissimilar results. This may ultimately lead to recommendations which can result in costly operations and unnecessary equipment deployment. However, when numerical modelling and geological methods are used in conjunction with one another, the results present a more realistic and practical view of the formation sands and their potential for solids production during the life of the well. Introduction As an increasing number of fields around the world enter their mature stages of production, the impact of depletion and increasing water cut is having a dramatic effect on their propensity for sand production. It is estimated1 that by 2010, half of all production wells and one third of injectors will produce sand. There is continuing demand for improved technologies to mitigate solids production as the industry strives to extract hydrocarbons from deeper, hotter wells in increasingly hostile environments. This is being met by improved gravel pack placement techniques and advanced expandable technologies as well as the proven methods of sand control. If the factors which contribute to sedimentary rock strength were few and constant, then all sandstones would be of similar strength and a reliable and universally applicable methodology for sanding prediction would now be in place. This is, of course, not the case and is what makes the accurate prediction of sand behaviour somewhat unpredictable. However, there remains uncertainty as to the accuracy of geomechanics work utilised in qualifying and quantifying a given well's propensity for sanding. This process is widely acknowledged; that is, the determination of the formation strength and impact of the in-situ stresses identifying the conditions under which failure of the rock will occur. A typical sand prediction model structure is shown in Fig 1.

Sand control operations and particularly those using granular filter media such as gravel packs and frac & pack are being carried out in increasing numbers and in more demanding environments. Improvements continue to be made in terms of equipment, fluids and operations. However, with the increasing emphasis on well productivity and minimizing impairment, it is clear that a better understanding of some of the current causes of impairment is required.The design of sand control filter media continues to be based on a limited number of discrete formation samples that are taken to be fully representative of the actual grain sizes throughout the interval of interest. It is often difficult to clearly identify the causes and location of the impairment unless expensive evaluation tools such as PLTs are utilized. This paper presents the results of research work that have successfully resulted in an analytical tool and a new granular system that allows improved design and evaluation of sand control operations. A system for the determination of grain size and pore blocking mechanisms on a foot-by-foot basis has been developed. Furthermore a granular filter media has been devised such that permeability damage from solids migration can be reversed. The results presented are based on "flow of solid particles through porous media" principles. The work included laboratory t esting for various gravels and these results are also included. Field validation was carried out with data from LDAs and an offshore deviated well.

The mature Kinabalu oilfield is currently producing 18,000 bopd from a peak of 40,000 bopd in 1998. Field rejuvenation plans include drilling and completing new infill and development wells from both the existing platform and a new platform. Most platform wells are currently producing sand and none have been completed with sand control. Although current levels are less than 10 pptb, sand production has caused erosion issues and lost production due to the need for regular separator clean outs on the existing platform. Sand production is therefore a key risk factor for both existing well integrity and new well completion design. An integrated, practical and pragmatic sand management strategy was developed founded on establishing the causes of sand production, predicting the conditions for sand failure, and ranking both passive and active sand control options. 1D geomechanical models were built from field, core and well data. The sand failure analytical model was initially calibrated against existing well sand production records, then run for the proposed new wells to assess the potential for sand production over the remaining field life. The model was also used to evaluate passive alternatives to active sand exclusion completions. Modelling supported field observations that sand production is closely linked to reservoir depth, completion style, well inclination and, most importantly, depletion level – sand production is unlikely at initial pressure conditions but is triggered by depletion. The sand failure analyses were embedded in an objective screening protocol which was developed to rank sand control options. This considers existing and proposed well completion architecture, facilities design/limitations, and recognises inherent data uncertainties. This systematic methodology allows a consistent, objective and transparent view of benefits and risks across the different sand control system aspects. Key selection criteria were utilised rather than arbitrary decisions based on limited and often unaudited data. The process ensured a best practice, fit for purpose, and structured sand management solution. As the current levels of sand production remain low, and in response to the challenges associated with remedial or retro-fitting sand control, optimised surface sand management will continue to be the preferred solution for all existing wells. Improved bean up procedures have already reduced sand production at well start up after a shut down. Sand production in most new infill and development wells is predicted to be manageable. In the higher risk wells, targeting shallower or weaker sands, installing sand control would be the default position. Yet re-thinking the completion design, optimising surface sand management procedures, managing drawdown and BHFP levels, and taking advantage of favourable stress vectors through oriented perforation can extend the sand free well operating envelopes over life of well production and depletion conditions, reducing or deferring the need for sand control in all but the highest sanding risk reservoirs. The first infill well to be completed with oriented perforations in Kinabalu produced at 2500 bopd on test with minimal levels of sand. Installing downhole pressure gauges in infill wells have improved BHFP control within the critical well pressure operational envelope from the sand failure model. To date the wells have shown significantly lower sand production than historically seen on Kinabalu production wells. Background Field Details The Kinabalu oil field, located 55 km west-north-west of Labuan, Malaysia, consists of three separate accumulations: Kinabalu Main, Deep, and East (Fig. 1). The bulk of the reserves are in the multiple stacked shoreface Miocene sands (F, J, K, L, M, and O) in Kinabalu Main.