Impact of Intelligent Well Systems on Total Economics of Field Development
Abstract: TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractIntelligent well technology, referring to the implementation of fundamental process control downhole, has advanced rapidly over the last decade in the upstream oil and gas industry. Application of this technology has continued to expand since recent installation results have demonstrated the value of these completions with a high success rate that operators find attractive.In this paper, we present an economic evaluation procedure to quantify the benefit of I… Show more
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Cited by 8 publications
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Throughout the past decade, the reservoir management and interventionless flow control benefits of Intelligent Well Systems have made them a perfect fit for deepwater developments. Approximately 90% of current deepwater wells are subsea, and the number of subsea wells is expected to continue to grow. To enable subsea operators to reap the rewards of intelligent well technology, the industry (operators and service companies) is working to interface downhole intelligent well equipment with subsea trees and controls. Currently, the hydraulic penetration requirements of intelligent wells and the limited number of hydraulic penetrations in many existing subsea trees prohibit some subsea operators from using intelligent well technology. Manufacturing lead times for subsea trees and control systems are usually quite long. Rather than interrupt rig and operation schedules for an extended period while waiting for new equipment with more penetrations, operators often choose not to run intelligent well systems, and sacrifice the resulting benefits. This paper will address various technologies and methodologies that are currently available to enable operators to benefit from intelligent well technology in subsea wells with limited number of penetrations. The case histories covered will illustrate how it is possible to reduce the number of hydraulic control lines required to remotely operate downhole flow-control valves without sacrificing overall system reliability. Introduction The industry has generally defined Intelligent Wells as wells equipped with downhole remote flow-control devices used to open, close, or regulate flow from and to multiple zones without the need for well intervention. Furthermore, Intelligent Wells are usually complemented by downhole permanent monitoring systems which provide valuable information used in the decision making process for the control of production or injection. All these systems require multiple control lines and cables to link the downhole tools to the associated surface equipment which serves as the interface between the operator and the system. Subsea systems are employed in deepwater applications or in shallow water fields where the economics do not justify the construction of dedicate platforms to support the wells. In subsea systems, the wellhead and Christmas trees are installed on the seabed and are submerged in the water, hence the name "wet trees." Wet trees, just like the surface "dry trees," provide a means of controlling the wells through a series of valves, piping, chokes and other related equipment. Subsea trees can be manually controlled by divers (shallow water operations) or by remote-control systems by means of hydraulic actuators. These control systems can be on surface linked to the trees by means of dedicated lines in an umbilical or they can also be sophisticated electro-hydraulic multiplex systems mounted on the trees, controlled through a subsea electronic module. Electro-hydraulic multiplex systems are becoming more popular due to faster response time, increased reliability, and lower umbilical costs. These subsea control systems not only need to control functions on the trees, but also need to be able to interface with and control downhole equipment (i.e. safety valves, downhole chemical injection valves, permanent instrumentation, and intelligent well valves). Penetrations through the tubing hanger provide a means of communication between the subsea control system and the downhole equipment. Subsea control systems normally have two hydraulic circuits for controlling downhole functions: one high pressure (HP) normally dedicated for the safety valve and one low pressure (LP) normally used for the intelligent flow control valves.
Throughout the past decade, the reservoir management and interventionless flow control benefits of Intelligent Well Systems have made them a perfect fit for deepwater developments. Approximately 90% of current deepwater wells are subsea, and the number of subsea wells is expected to continue to grow. To enable subsea operators to reap the rewards of intelligent well technology, the industry (operators and service companies) is working to interface downhole intelligent well equipment with subsea trees and controls. Currently, the hydraulic penetration requirements of intelligent wells and the limited number of hydraulic penetrations in many existing subsea trees prohibit some subsea operators from using intelligent well technology. Manufacturing lead times for subsea trees and control systems are usually quite long. Rather than interrupt rig and operation schedules for an extended period while waiting for new equipment with more penetrations, operators often choose not to run intelligent well systems, and sacrifice the resulting benefits. This paper will address various technologies and methodologies that are currently available to enable operators to benefit from intelligent well technology in subsea wells with limited number of penetrations. The case histories covered will illustrate how it is possible to reduce the number of hydraulic control lines required to remotely operate downhole flow-control valves without sacrificing overall system reliability. Introduction The industry has generally defined Intelligent Wells as wells equipped with downhole remote flow-control devices used to open, close, or regulate flow from and to multiple zones without the need for well intervention. Furthermore, Intelligent Wells are usually complemented by downhole permanent monitoring systems which provide valuable information used in the decision making process for the control of production or injection. All these systems require multiple control lines and cables to link the downhole tools to the associated surface equipment which serves as the interface between the operator and the system. Subsea systems are employed in deepwater applications or in shallow water fields where the economics do not justify the construction of dedicate platforms to support the wells. In subsea systems, the wellhead and Christmas trees are installed on the seabed and are submerged in the water, hence the name "wet trees." Wet trees, just like the surface "dry trees," provide a means of controlling the wells through a series of valves, piping, chokes and other related equipment. Subsea trees can be manually controlled by divers (shallow water operations) or by remote-control systems by means of hydraulic actuators. These control systems can be on surface linked to the trees by means of dedicated lines in an umbilical or they can also be sophisticated electro-hydraulic multiplex systems mounted on the trees, controlled through a subsea electronic module. Electro-hydraulic multiplex systems are becoming more popular due to faster response time, increased reliability, and lower umbilical costs. These subsea control systems not only need to control functions on the trees, but also need to be able to interface with and control downhole equipment (i.e. safety valves, downhole chemical injection valves, permanent instrumentation, and intelligent well valves). Penetrations through the tubing hanger provide a means of communication between the subsea control system and the downhole equipment. Subsea control systems normally have two hydraulic circuits for controlling downhole functions: one high pressure (HP) normally dedicated for the safety valve and one low pressure (LP) normally used for the intelligent flow control valves.
One of the main drivers of field development is maximization of oil reserves. The value of assets and therefore companies is strongly linked to the amount of producible reserves of their holdings. Traditionally the full potential of the reservoir is locked due to a series of limitations both at the sub-surface and surface. Increasing in oil demand challenges the development not only to improve on oil recovery but also boost the near term production. Subsurface models are extensively used to determine the optimum development strategy for the field, infill wells are used to target un-swept areas of the reservoir, while water and or gas injection may be used to preserve reservoir energy. In comparison surface facilities are not so extensively looked after especially in an offshore environment, and often times only a de-bottlenecking of the optimum sub-surface case is performed. The integration between surface network modeling and subsurface modeling is critical to ensure field operation is in line with reservoir management and the facility is adequate to handle the expected production. This paper discusses the various stages of optimization, using numerical simulation combined with a surface model, to determine the impact of surface operations in overall field performance. The results allowed shifting of the resources to further understand the surface operations which affect the overall field performance as well as identifying near term production enhancement opportunity. This work shows how an effective combination of reservoir energy preservation by means of upgrading the current surface facilities and adding optimized existing wells accounts for as much as 50% of the total potential recoverable reserves. Furthermore, after evaluating each development options, a matrix risk is formulated to take into account not only the quality and quantity of the data but also the degree of man interventions during the life of the field (surface optimization). Value-of-information figures were then associated to each of the suggested new data/equipment to help prioritize the development As a result measurement efforts were carried out including horizontal production logs to minimize uncertainty of the reservoir contribution.
Investigating the Effect of the Placement of Permanent Downhole Pressure Gauges in Intelligent Well Systems on Well Productivity: A Field Example
In developing most deepwater fields with limited number of wells, intelligent well systems which consist of many valves and sensors are employed to maximize production capacity under facility constraints. Analysis of sensor data unaffected by wellbore effects allows operators to estimate key reservoir parameters, well capacity and calculate actual flow rates at zonal level. Decisions for operational control is made based on data analysis, the result of which is used to optimize overall field performance and maximize return on investment. Understanding pressure sensors placement issue is important from pressure-transient analyses viewpoint. Pressure gauges should ideally be placed as close to the perforations as possible to ensure the pressure data is unaffected by friction in the tubing between the perforations and pressure gauges but placement of the gauge is dictated by completion hardware configuration and can be located far away from the point of reservoir fluid entry. This may result to potentially erroneous measured pressure data and may lead to the calculation of inaccurate reservoir parameters and an overestimated mechanical skin value from pressure buildup response. One of the main operating constraints in deepwater wells is flux limit which is a practical well surveillance tool used to monitor and operate sand control completions, maintaining each producing interval at a maximum safe operating rate, and also monitoring well impairment to allow for proactive remedial operations. Since the flux limit is a function of mechanical skin, if the mechanical skin is over estimated because frictional losses are not properly accounted for, well production may be unnecessarily constrained. In this paper, analysis was done using a wellbore/reservoir simulator to account for frictional effects in the tubing between the perforations, and the gauge for a field example. Sensitivity analysis was also carried out at different flow rates for each well and simple correlations were developed for predicting frictional effects. Results obtained from calculations showed that pressure gauges placement effect is significant as flow rate and gauge distance from perforations increases. Correcting for this effect increased the flux limit thus increasing production rate on several wells that were previously flux constrained.
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