Best Cleanup Practices for an Offshore Sandstone Reservoir with ICD Completions in Horizontal Wells
Abstract: Achieving effective cleanup while flowing back the well after drilling is key for maximizing productivity and minimizing near wellbore damage. This paper discusses the best practices for cleanup in a sandstone reservoir drilled with oil-based mud (OBM), and installed with inflow control device (ICD) completions. The findings are based on the evaluation of different cleanup methods: coiled-tubing deployed nitrogen kickoff, chemical treatments, artificial lift-electric submersible pump vs. natural flow, time spe… Show more
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Cited by 11 publications
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Effective well cleanup during well start-up ensures efficient formation damage removal and maximises the resulting well production potential. Horizontal wells are more susceptible than vertical wells to formation damage due to the longer completion length, the longer drilling time, the potentially increased overbalance and the reduced cleanup efficiency caused by the heal-toe effect. Extensive modelling and simulation work has been previously performed analysing the impact of formation damage and well cleanup in horizontal wells. This paper extends that work to advanced completions employing Interval Control Valves (ICVs) and Inflow Control Devices (ICDs). It reports a comparative study that illustrates the greater cleanup efficiency of advanced, long horizontal well completions over that achieved by the equivalent, conventional, openhole completion. The highest cleanup efficiency is predicted to be achieved by an intelligent completion employing both sensors and ICVs. The well's full production potential will only be realised if a proper, real-time, cleanup monitoring and control procedure is implemented to optimise the choking strategy. Only then will the near wellbore cleanup efficiency be maximised. A dynamic well simulator has been used to illustrate the advantages of employing such a proper, real-time, cleanup monitoring and choke control strategy. This only becomes possible if an intelligent completion is employed. Sensitivity analysis is used to illustrate how an ICV completion gave the highest cleanup efficiency for almost all the parameters studied. The single zone cleanup strategy employed by an intelligent completion requires that extra time be spent on the initial stages of the cleanup process. Guidelines are required to ensure economic as well as technical optimisation of the cleanup process. This can be achieved by use of the presented, practical downhole monitoring procedures for efficient well cleanup together with a novel procedure for identifying the time when the near wellbore region is sufficiently clean. 1.0 Introduction Formation damage is one of the major factors controlling actual well productivity 1. This is especially true for long, horizontal wells that have been drilled and completed overbalance with water-based fluids 2, 3. Perforating may bypass the contaminated zone, but is itself susceptible to damage. It has been long recognised that well cleanup complications increase with increasing well length and number of completion zones. Cleanup management has been recognised as essential for successfully bringing the well on production with the highest possible production potential. Recent publications 4, 5 provided a qualitative discussion on cleanup as part of a comparative framework for the evaluation of the strengths and weaknesses of advanced and conventional completions. This paper sets out to quantify the advantages of advanced completions to improve cleanup by use of their permanently installed, downhole flow control equipment and measurement sensors. Intelligent wells add additional value by providing more effective cleanup than conventional ones. Subdividing the total producing length into a number of zones which are opened successively during the well start-up period is a field proven practice that maximises the drawdown to a particular zone and minimises the chance of flow conduit blockage by deposition of produced sand. The increased drawdown created by unloading the separate well zones sequentially leads to more effective formation cleaning. This temporary zonation of the wellbore can be achieved with specially pre-installed devices (e.g. clean-out or sandface valves). Real-time, downhole pressure data can be used to ensure that the flowing bottomhole pressure is kept above the sand production limit 6. Intelligent wells break the completion into a number of zones with downhole valves while their multiple gauges can be used to control and monitor the zonal production. They also have the additional capability of optimizing the cleanup operation. This paper will first discuss the processes that cause formation damage in the near wellbore area due to drilling and completion fluids. We will then compare the conventional well's success in cleaning up this damage with that of an advanced well completed with either Interval Control Valves (ICVs) or Inflow Control Devices (ICDs). Finally we will develop recommendations for improved cleaning techniques.
Effective well cleanup during well start-up ensures efficient formation damage removal and maximises the resulting well production potential. Horizontal wells are more susceptible than vertical wells to formation damage due to the longer completion length, the longer drilling time, the potentially increased overbalance and the reduced cleanup efficiency caused by the heal-toe effect. Extensive modelling and simulation work has been previously performed analysing the impact of formation damage and well cleanup in horizontal wells. This paper extends that work to advanced completions employing Interval Control Valves (ICVs) and Inflow Control Devices (ICDs). It reports a comparative study that illustrates the greater cleanup efficiency of advanced, long horizontal well completions over that achieved by the equivalent, conventional, openhole completion. The highest cleanup efficiency is predicted to be achieved by an intelligent completion employing both sensors and ICVs. The well's full production potential will only be realised if a proper, real-time, cleanup monitoring and control procedure is implemented to optimise the choking strategy. Only then will the near wellbore cleanup efficiency be maximised. A dynamic well simulator has been used to illustrate the advantages of employing such a proper, real-time, cleanup monitoring and choke control strategy. This only becomes possible if an intelligent completion is employed. Sensitivity analysis is used to illustrate how an ICV completion gave the highest cleanup efficiency for almost all the parameters studied. The single zone cleanup strategy employed by an intelligent completion requires that extra time be spent on the initial stages of the cleanup process. Guidelines are required to ensure economic as well as technical optimisation of the cleanup process. This can be achieved by use of the presented, practical downhole monitoring procedures for efficient well cleanup together with a novel procedure for identifying the time when the near wellbore region is sufficiently clean. 1.0 Introduction Formation damage is one of the major factors controlling actual well productivity 1. This is especially true for long, horizontal wells that have been drilled and completed overbalance with water-based fluids 2, 3. Perforating may bypass the contaminated zone, but is itself susceptible to damage. It has been long recognised that well cleanup complications increase with increasing well length and number of completion zones. Cleanup management has been recognised as essential for successfully bringing the well on production with the highest possible production potential. Recent publications 4, 5 provided a qualitative discussion on cleanup as part of a comparative framework for the evaluation of the strengths and weaknesses of advanced and conventional completions. This paper sets out to quantify the advantages of advanced completions to improve cleanup by use of their permanently installed, downhole flow control equipment and measurement sensors. Intelligent wells add additional value by providing more effective cleanup than conventional ones. Subdividing the total producing length into a number of zones which are opened successively during the well start-up period is a field proven practice that maximises the drawdown to a particular zone and minimises the chance of flow conduit blockage by deposition of produced sand. The increased drawdown created by unloading the separate well zones sequentially leads to more effective formation cleaning. This temporary zonation of the wellbore can be achieved with specially pre-installed devices (e.g. clean-out or sandface valves). Real-time, downhole pressure data can be used to ensure that the flowing bottomhole pressure is kept above the sand production limit 6. Intelligent wells break the completion into a number of zones with downhole valves while their multiple gauges can be used to control and monitor the zonal production. They also have the additional capability of optimizing the cleanup operation. This paper will first discuss the processes that cause formation damage in the near wellbore area due to drilling and completion fluids. We will then compare the conventional well's success in cleaning up this damage with that of an advanced well completed with either Interval Control Valves (ICVs) or Inflow Control Devices (ICDs). Finally we will develop recommendations for improved cleaning techniques.
Formation damage created during drilling or workover operations significantly reduces the performance of many wells. Long, horizontal and multilateral wells crossing heterogeneous, possibly multiple, reservoirs often show greater formation damage than conventional wells. This is partly due to the longer exposure of the formation to the drilling and completion fluid due to the well geometry as well as to the greater overbalance pressure often applied during drilling such wells and poorer cleanup. The typical well clean up process involves flowing the well naturally or aided by artificial lift to remove the external and internal mudcake and flow-back the mud filtrate. This process can be effective in conventional wells but is not adequate in long horizontal and multilateral wells suffering from increased frictional pressure drop along the wellbore and heterogeneity. The cleanup efficiency is improved by employing Advanced Well completions. Inflow Control Valves (ICVs) control the contribution from individual laterals or a specific zone along the extended horizontal wellbore. Inflow Control Devices (ICDs) equalise the contribution along the (long) completion length. In addition, Autonomous ICDs can manage the influx of unwanted fluids. This paper studies the cleanup performance of such wells completed with these advanced, downhole flow control technologies. It provides valuable insights into how these completions improve the well cleanup process and compares the ability of (A)ICD and ICV technologies to provide the optimum:Drawdown to lift off the filter cake formed by different mud systems (without causing sand production).Recovery rate of the invaded mud filtrate. Guidelines for Advanced Well Completion cleanup along with simulated results of synthetic and real field cases are included. 1 Introduction Formation damage is a deterioration of the near wellbore, reservoir formation characteristics. It has been described as: "The impairment of the invisible, by the inevitable and uncontrollable, resulting in an indeterminate reduction of the unquantifiable" [1]. Its causes include: "physico-chemical, chemical, biological, hydrodynamic, and thermal interactions of porous formation, particles and fluids and mechanical deformation of formation under stress and fluid shear" [2]. These processes can be triggered at all stages of the well or field's life: drilling, workover, completion, gravel packing, production, injection, stimulation, etc. Formation damage reduces the absolute formation permeability and/or causes an unfavourable relative permeability change; both of these will adversely impact the well and reservoir performance. Increasing the well-reservoir contact has become an increasingly popular well construction option. It brings a number of potential advantages - increases in the well productivity, drainage area and sweep efficiency plus delayed water or gas breakthrough. Drilling, workover and (re)completion are all major interventions that result in severe formation damage in Extended Reservoir Contact (ERC) wells. External and internal mudcakes are often formed at the sandface in addition to mud filtrate invasion into the near wellbore area during these interventions. Increased levels of formation damage is to be expected in ERC wells compared to conventional wells due to the increased exposure to the reservoir, use of a higher overbalance pressure and the increased time required to drill and complete these wells. Both water and oil based mud are used to drill ERC wells. Polymers are added to these mud systems to enhance their ability to suspend drill cuttings within the long and tortuous wellbores so that they can be circulated to surface. These polymers will absorb on water wet, formations; altering the irreducible water saturation around the wellbore and complicating the water based filtrate's flow back during the cleanup process.
Passive completions, comprised of inflow control devices and external packers, are usually considered in horizontal wells, located in risky or mature areas. These completions are proven techniques for reservoir conformance to mitigate water or gasconing problems and ensure uniform production contributions along the horizontal section. After well completion or shortly after initial production, these wells may fail to sustain production, largely due to formation damage or plugging in the inflow control devices. The conventional acid program, applied on wells with non-passive completions, is not suitable on these wells, due to the risk of impacting the completion integrity to the extent that it will violate the installation purposes. The requirements of acid treating wells with the same completions become inevitable due to the increasing number of wells equipped with these completions in a major carbonate reservoir in Saudi Arabia. A smart approach has been developed through innovative thinking to stimulate wells equipped with passive completions. The new approach has successfully stimulated four wells and resulted in restoring well productivity. This smart stimulation approach demonstrates a competent method to clean out the ICD completion along the horizontal section and to remove formation damage.
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