Artificial Lift Technologies and Their Relevance in Production Optimization - Term Paper Example

Artificial lift technologies and their relevance in production optimization Name Institution Subject Instructor Date Abstract Tools used in the optimization of the wells revolve around the value that calls for proper monitoring of the reservoir changes. This involves the quantification of data well as controlling the manner in which the state of the well. Analysis of the artificial system involves the operation of the work flows. Use of artificial lift technology has been utilised in meeting the [production challenges that aims in the optimization of power and reliability improvement. Current technologies calls for the utilization of alternative means that would be utilized in the productive lift systems in the fields. The mostly used artificial lifts utilized the gas and the jet pumps that have combined the electric pumps which are submersible. Utilization of SPE focuses on the make to order mode of manufacturing model that comprises the various mix of low and high volume products. This paper elucidates the advantages and disadvantages of artificial lift technologies and their relevance in the production optimization. Table of Contents Table of Contents 3 1 Introduction 4 1.1Production of oil well 5 2 Artificial lifts 7 2.1Rod lifts 7 2.2The progressive cavity pumps 8 2.3 Subsurface Hydraulic Pumps 9 2.4 Electric Submersible Pumps (ESPs) 11 2.5 Gas lift 11 3 Why adopt artificial lift systems 12 4 Current developments 13 5 Workover and Restart- The Marimba Field VASPS prototype 13 6 Conclusion 14 1 Introduction Firstly, most parts in the world sit on huge deposits of oil, sand and natural gas which were not being utilized before but things have changed and these ‘uneconomic’ resources are being transformed into economically usable products, which can be said to be driving the world economy as noted by Clegg (2007). As the world races to harness the resources, there has been unparalleled need for innovation and technological advancements to ensure that these products are harnessed economically at lesser costs and ensuring that most of the gas has been brought to the surface. Additionally, as noted by Lloyd (2009), large oil and gas exploitation companies such as; `Weatherfold’ and `Sclumberger’,among others have been at the forefront to come up with technologies which ease the lifting of heavy oil and gas from the earth deposits to the surface. The immense development in the oil exploitation industry of late has been orchestrated by the movement of oil mining to onshore, the depletion of light-oil projects and the migration of producers to deep water offshore mining. On the other hand, Dickey (2007) defines that, an artificial oil lift is a system whose sole intent is to increase energy (head) in the oil column in the bore so as, to start and improve the movement of the fluid from the well. The artificial lifts use a wide range of working principles which include but not limited to rod pumps, gas lifts and submersible pumps. 1.1Production of oil well Once an oil well has been diagnosed and assessed as having economically viable deposits, the Engineers start pondering on the best methods to be used to maximize the recovery of the oil. Gas and oil is found in pores of reservoir rocks, some types of the rocks allow the oil and gas to move freely in the pores thus allowing easy oil recovery. Other reservoir rocks do not allow easy movement of oil and thus, call for advanced technologies to move the oil and gas from the reservoir rock pores to the well. It is worth noting that, even with today’s advanced technologies, more than 60 percent of the oil in some reservoirs is not possible to recover (Bradley and Richardson, 2006). Before a well can bring oil to the surface, the bore is first stabilized with a casing. This casing contains a number of pipes which are cemented to position. The casing is intended to protect water from coming into contact with oil thus leading to contamination. A tubing string held in position is centered on the well bore; this tubing is the one which brings the gas and oil from the reservoir to the surface. In the reservoir, there are elevated pressures as a result of the underground forces. The driving forces inside the oil/gas reservoirs either water or gas drive. The water drive reservoir is bonded to an active aquifer which gives the driving mechanism. For the gas driven reservoir, the energy is from expansion of the gas mainly from gas cap or the breaking out of solution as noted by Mahoney (2006). During the early production years, the underground pressure will force the oil up the bore to the surface and this phenomenon is referred as natural flow. In the event that the pressure difference can not lift the hydrocarbons up the bore, some artificial lifting methods like pumps are used. Fig a. Water drive reservoir (Bradley and Richardson, 2006) Fig b. gas drive reservoir (Bradley and Richardson, 2006) Fig a Fig b Most of the well will follow a curve in production meaning that production will increase steadily for some time, then level and decline. The length of the decline curve is affected by the condition of the well, some of the well produce for a short period while others extend their production for more than 100 years like Iraq (Lloyd, 2009). During the decline period, the petroleum engineers do’ work over’ which includes the cleaning of wellbore to necessitate easy movement of oil and gas to the surface. The reservoir rock may also be fractured and treated with acids to increase its permeability and allow easy movement of gas and oil. Another technique referred to as waterflooding may be used (Clegg, 2007). Here, the production wells are changed to injection wells where water is injected into the well to bring out oil. In the advanced ages of the oilfield, an advanced technique referred as Enhanced oil recovery is applied. Here various substances including steam, surfactant and carbon dioxide gas is injected into the reservoir to increase the production. All the time, the oil wells will produce a mixture of oil, gas and water which are separated at the surface, but as time goes by, the water content becomes high; this increased water percentage necessitates the need for an artificial lift (Lloyd, 2009). The pressure in the column surpasses the reservoir pressure thus the well cannot use natural flow hence an artificial system becomes necessary. 2 Artificial lifts The artificial lifting methods used in oil and gas exploitation fall in either the pump or gas lifts. The pump lift systems are: rod lifts, the progressive cavity pumps, the subsurface hydraulic pumps and the electric submerged pumps. 2.1Rod lifts The rod type artificial lift usually makes use of positive displacement pump usually put or set at tubing at the bottom of the well. The plunger of the pump is connected to the surface using a long string referred as sucker rod and driven by a beam unit at the surface. Every upstroke of the beam unit will move the oil above the plunger of the pump. Advantages of the Rod Lift system It has been proved to have high efficiency. It is cheap to repair service and maintain. It has a strong drawdown. There is availability of optimization controls. There is high salvage value. It is possible to adjust production by varying stroke lengths and speeds. Disadvantages Is limited to low production volumes, levels below 1,000 barrels a day A Beam Pumping Unit (Lloyd, 2009) 2.2The progressive cavity pumps These types of lifts are composed of three components. These are the surface drives, the drive strings and the downhole PC pumps as noted by Dickey (2007). The PC pump has one helical rotor which turns inside double a stator which is elastomeric lined. This stator is connected to a production string and it does not move during pumping. In most times, the rotor is connected to a sucker rod suspended and has a surface drive to rotate it. Once the rotor turns in the stator, sealed cavities are formed and they advance from the inlet to the discharge end of the pump. The result of this is a constant positive displacement flow whose discharge is proportional to the cavity size, the speed of rotor and the pressure difference in the pump. In some cases, the progressive cavity pumps don’t use sucker rod strings and surface drives but are connected to Electric submersible pump motors. Advantages of Progressive Cavity Pumps They need less capital investment There is increased system efficiency Less noisy Less power usage Portable and light surface equipment They have no internal valves which might clog or lock the gas Can pump heavy oils The disadvantages They are limited to pumping heights of 7,000 feet. 2.3 Subsurface Hydraulic Pumps The hydraulic lift systems are composed of a power fluid system on the surface, a prime mover, a reciprocating pump and a downhole jet (Clegg, 2007). During the operation of this lift system, power fluid which may be crude oil or water is moved from a reservoir storage tank and fed to the surface pump. The power fluid is under pressure which comes from the surface pump and under control from the valves at the control station and is distributed to a single or more wellheads. The oil or water will pass through the valve on the wellhead and be directed to the downhole pump. In an installation using piston pump, the engine is actuated by the power fluid, which will drive the pump and the power fluid will come to the surface together with the produced oil, then it will be separated and pumped to the storage tank. The jet pump on the other hand has no moving parts and hence uses the Venturi principle to bring the oil to the surface using the fluid pressure. Advantages of Hydraulic lift system In this case, each case has the following advantages The jet lifts It has no moving parts. The maintenance costs of the pump are low. It has great volume capacity. It is possible to have multiwall production from a single unit. The piston lift system Has strong drawdown High volumetric efficiency It can be applied to great depths-up to 15,000 feet The disadvantages of hydraulic lift system It requires immense capital cost It is complicated to operate It becomes economical in cases where we have a number of wells together in a pad In case there arises a problem with the surface or prime over, then all well become out of operation b) Jet hole pump a) Down hole piston type pump 2.4 Electric Submersible Pumps (ESPs) This system has an electric motor and a centrifugal pump connected to surface control mechanism and a transformer via an electric power cable. In this system, the down hole components are usually suspended above the wells’ perforations from the production tubing while the motor is fixed on the bottom of the work string. The pump, the seal section and the gas separator is found above the motor (Dickey, 2007). The cables are banded to the tubing and plugs into the motor leads. As the fluid gets into the well, then, it must pass through the motor into the pump. The movement of the fluid past the motor helps in cooling of the motor. Then fluid enters the intake into the pump. Each stage results into addition of pressure or head to the fluid. The fluid will gather sufficient pressure as it reaches the pump to move it to the surface into the flow line. These pumps are mainly used in high volume oil lifting applications i.e. 1,000 barrels per day. Advantages They have high efficiency Low maintenance costs High resistance to corrosion Disadvantages It’s not possible to pump sand 2.5 Gas lift In this system, gas at high pressure is injected into production string through gas lift mandrels and valves. This gas will reduce the hydrostatic pressure in the string to establish the needed pressure difference between the bore of the well and the reservoir and hence the fluids flow to the surface. The fluids weight is reduced by the gas and thus the reservoir pressure forces the fluids up. It is needed that we have a source of compresses gas for this operation. Installation is required to be one carefully in this system. Advantages It is an enhanced artificial lift method and thus it has improved efficiency It is used effectively where there are several wells which are utilised. Use of gas lift also suffices well in the scenario where there exists no market that would require the production of gases. It also serves well in places where electricity is not easily accessible. Disadvantages it is compulsory to have compressed gas high initial costs it is difficult to operate 3 Why adopt artificial lift systems It is prudent for a company to exploit as much resource as possible, increase its production efficiency while maintaining low costs and. A number of conditions of the oilfield will cause the mining company to adopt the new technology. These may be due to: long distance of transport of the oil the viscosity of the fluid maybe so high that the reservoir pressure cannot lift it up the surface The wells may be too deep thus need of artificial lift methods for the gas and oil. As the natural pressure will not provide sufficient head to the fluids the oilfield might be aged and thus having little reservoir pressure the reservoir rocks may be impermeable we might have high water cuts 4 Current developments In these mining operations, there are a lot of pressure losses in the surface multiphase gathering systems hence a good mixture/ combination of well pumps and surface pumps are needed to combat the losses and effectively lift the oil and gas to the processing unit. In the artificial lift phenomena, the main issues which have to be addressed by the petroleum engineers involve the handling of the sand produced during this operation, the ability to increase the volume of the produced gas and oil and the high localized temperatures which are associated with the heat recovery projects (Lloyd, 2009). The natural gas mining business is booming and hence attention is focused on artificial lift methods in the gas and the development of wet gas (Clegg, 2007). On the surface, there are imminent reductions of capital expenditures and complexity which occurs due to improved wet gas gathering systems thus boosting of the wet gas stream through the surface flow lines is of great importance. We usually have problems related to the lifting of gas and oil in the wellbores, which are known by the engineers here and currently, we have more creative and innovative techniques being applied. These entail the combining of chemicals to enhance the flow lines such as; sufficants and downhole enhancing tools. Deep water mining has also led to the advancements in the artificial lift systems. For the deep water mining, flow in risers and other subsea flow lines are eminent in the production system. 5 Workover and Restart- The Marimba Field VASPS prototype The VASPS, an acronym for Vertical annular separation and pumping system is a current innovative method of gas and oil separation techniques in subsea drilling. The VASPS is a new separation technique which is associated with Electrical submersible pump. In this method, after the liquid and gas mixture is separated after being passed through a helical channel, the liquid is pumped by the ESP while the gas is channelled to the platform (Lloyd, 2009). The operation at the subsea greatly lowers the bottom hole pressure needed for a particular production rate hence increasing the production capacity of a particular well. There was a joint projection done by AGIP, Exxon Mobil and Petrobras which developed and installed the VASPS to separate the production from a well MA-01, and hence produce semisubmersible platform P-08.the technology worked well up to December 2001 when a failure occurred, but this failure was not linked to the new VASPS technology but rather on the ESP system. It was repaired by Petrobras and started operations again. 6 Conclusion In conclusion, the artificial lift systems formally entailed the traditional methods of well pumping. This entailed the rod system, progressive cavity systems and gas lifts. But nowadays, this has changed because there are tremendous changes occurring in the oil industry. This is no longer limited to occurrences in oil well but encompasses methods used in the oil well and includes methods being used to lift the fluids up and transport to their respective destinations. References Bradley, H. and Richardson, T., 2006. Petroleum Engineering Handbook, Society of Petroleum Engineers, U.S.A. Clegg, J.D., 2007. Production Operations Handbook.SPE, USA. Dickey, M., 2007. Economic pumping technology for coal bed methane (CBM), stripper oil, and shallow gas well deliquification, Mexico. Lloyd R., 2009. Decision Tree for Selection of Artificial Lift Method, SPE 29510. Mahoney, M., 2006. New methods and equipment for dewatering unconventional gas resources using sucker rod pumping equipments, SPE 104547. Ohio Read More