Workover Rig Research Articles

Study on Hoist Force Calculation of Hydraulic Lifting System Used in Pressure Balance Workover Rig

Abstract. Pressure balance workover is an advanced downhole operation technique. It can hoist the strings of the tube or put it down under certain pressure. The research on pressure balance workover rig has become a hotspot in both domestic and overseas. Pressure balance workover operation technique has been widely used oversea. At the present time, relevant studies have been developed in China. In this paper, domestic and international technology status is fully analyzed, working principle of hydraulic lifting system is studied, then equivalent calculation model and calculation method of hoist force are put forward, calculation program of hoist force was compiled for the different oil pipe depth, curve and charts changing with the oil pipe depth are given, It provides a theory reference to field operation.

Material Property Analysis and Technology of Washover Permanent Packer

In order to adapt the use of workover rig for offshore completion and workover operations, it generally uses two different drive mode of milling, downhole motor and surface turntable, in dealing with deep inclined well permanent packer issues. In this thesis, the material property of pipe strings is analyzed and the axial forces, torques and frictions and other mechanical calculation models of the pipe string are established under two kinds of drive modes. Through the results of analysis of pipe string force, it analyzes the material property of permanent packer, optimizes the parameters of downhole tools and operation methods in milling operation.

A simple and robust Simulated Annealing algorithm for scheduling workover rigs on onshore oil fields

Onshore oil wells are dependent of maintenance services such as cleaning, reinstatement and stimulation. These services can be performed by a limited number of workover rigs. Usually, wells need maintenance services and a scheduling of the workover rigs must be defined. This scheduling must consider some factors such as the well production, the type of service to be performed and time windows for the service. There is a production loss associated to wells waiting for maintenance services, so it is important to attend them as soon as possible. Thus, the workover rig scheduling problem consists of finding the best schedule for the limited number of workover rigs, minimizing the production loss associated with the wells waiting for maintenance service. We present a simple and robust Simulated Annealing (SA) algorithm for solving this problem. Computational results on real problems obtained in Brazil are reported and SA presents better solutions than all those approaches reported in the literature.

Energy-recovering Workover Rig with Variable Inertia Flywheel

ABSTRACT An energy-recovering workover rig with variable inertia flywheel is investigated, and its basic structure and working theory are introduced. The variable inertia flywheel is composed of three identically sized flywheels with a mass of 458 kg each. It stores the energy of an idle motor as the tubing string is raised, as well as the potential energy released by the tubing string when it is lowered. The power of this rig decreases remarkably as compared to that of a conventional rig, and it can also recover and reuse the potential energy of the tubing string. The energy recovered by the flywheels is about 3.9×105 kJ when a 2500 m-long tubing string is lowered. The mathematical model for when the workover rig raises the tubing string is deduced, and simulation analyses are conducted. Through simulation, the curves of the rising velocity of the tubing string and displacement with time are obtained, and the following conclusions are reached: the heavier the tubing string, the lower the velocity of the ...

Module Partition Research for the Marine Drilling Rig

The modular design principle is that much more products are composed by fewness module, and the products should be stable, and have high precision, simple structure, and also lower cost based on the customer requirements, therefore, dividing and treating the level, size and number of the module scientifically and reasonably is an important guarantee for the successful modular design. And now the modular design based on the different thought, for the marine work-over rig, and scientifically rational module partition scheme are offered based on the principle and theory of the module design and module division, which has important significance for the design and development of the module rig.

Development of Hydraulic Control Jam Release Device for Workover

Developed a device used to assist workover rig in lifting stuck tubing strings from the well during workover treatment, it can create well economic benefit for oil field. The device adopts remote hydraulic control, which is safe and reliable. The structure and work principle of the device is illustrated. The jam release device is mainly made up of hydraulic cylinders, hydraulic pump and hydraulic control valves. With the coordination between lifting hydraulic cylinders and hydraulic slips, the device can lift tubing strings from the well. The important loading unit of the device is analyzed by finite element. The working pressure is made from 5MPa to 20MPa, corresponding to lifting force range of 229kN to 915.6kN, which can meet the jam release force in workover treatment.

A Grasp with Path-Relinking for the Workover Rig Scheduling Problem

Onshore oil wells depend on special services like cleaning, reinstatement and stimulation. These services, which are performed by a short number of workover rigs, are important to keep oil production as optimum as possible. Consequently, scheduling must be determined, where several factors interfere, such as production, service to be performed on each well, and time windows for each service. When a well needs service, its production is interrupted. In this regard, the workover rig scheduling problem consists of finding the best sequence of wells, which minimizes the production loss associated with the wells waiting for maintenance. In this paper, the authors present a Greedy Randomized Adaptive Search Procedure (GRASP) with Path-Relinking (PR) to solve this problem. Computational results are obtained from real problems of a Brazilian oil field.

Integrated Approach to Formation-Water Management: From Reservoir Management to Protection of the Environment

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 116218, "The Integrated Approach to Formation-Water Man agement: From Reservoir Management to Protection of the Environment," by Jose G. Flores, SPE, and Jon Elphick, SPE, Schlumberger, and Francisco Lopez and Pablo Espinel, Agip Oil Ecuador, prepared for the 2008 SPE Annual Technical Conference and Exhibition, Denver, 21-24 September. The paper has not been peer reviewed. Most fields in the Oriente basin of Ecuador and neighboring Marañón and Putumayo basins in Peru and Colombia, respectively, produce large volumes of water. In most cases, as the water cut increases, oil production is restricted, which creates production problems including scale deposition, corrosion, and sand production. An integrated approach to formation-water management begins with an understanding of the water-flow mechanisms in the reservoir and identifying the water-breakthrough mechanism at the producer well, followed by the detection of production bottlenecks in the wellbore and surface facilities, and then finishing with analysis of water disposal or reinjection. Introduction Villano is a heavy-oil field in a tropical rainforest area in the Province of Pastaza in the Oriente basin of Ecuador. Discovered in 1950, it began producing in 1999. Because of concern for the environment and native communities in the area, development was performed in an offshore-type fashion. With no road access, all transport was provided by helicopter. The drilling and production facilities are limited to two well pads, V-A and V-B of approximately 4 and 2 hectares, respectively. Pad V-A hosts a drilling and a workover rig, drilling warehouses, well pads, living quarters, production facilities to dehydrate the oil, and transfer pumps to transport the oil through a 12-in.-diameter 44-km-long pipeline to the central processing facility (CPF). Formation water is disposed of at Pad V-A into two water-disposal wells (WDWs). Pad V-B is a remote wellsite with limited facilities. Particularly relevant in the effort was construction of the aerial 12-in. pipeline, built without road support and with a minimum effect to the rain forest environment. The Villano structure was developed primarily with horizontal wells. Sixteen wells have been drilled in Villano—13 producers, all fitted with electrical submersible pumps (ESPs); two WDWs; and one discovery well (V-1), which has been abandoned. There are two additional WDWs at the CPF. All the production is from and water disposal is into the Hollín formation, of Cretaceous age.

Improving Well Safety With an Innovative Surface-Controlled Subsurface Safety Valve

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper SPE 113829, "Improving Well Safety and Maximizing Reserves Using an Innovative Surface- Controlled Subsurface Safety Valve (SC-SSSV)," by Francois Millet, SPE, Harve Petit, and Gery Wallez, Geoservices Equipment, and Philippe LaLanne, Alain Ducasse, and Emile Barzu, Total E&P France, originally prepared for the 2008 SPE Annual Technical Conference and Exhibition, Denver, 21-24 September. The paper has not been peer reviewed. A common cause of failure of surface-controlled subsurface safety valves (SCSSSVs) is a defect in the downhole hydraulic line that controls the valve from the surface. Such a failure generates production losses and requires the intervention of a costly workover rig. To alleviate this type of situation, a system has been developed in which the physical control line has been replaced by a communication system based on electromagnetic (EM) waves. The surface emitter continuously sends a signal to the SCSSSV. Both are designed to be fail-safe. Introduction Lacq field was developed from 1951 to 1957, while solving metallurgical constraints caused by the 15% H2S and 10% CO2 in its gas composition. Nearby, three other fields produce the same long and narrow reservoir and started production in late 1967. From 1968 to 1982, gas production reached approximately 33×106 m3/d, the production from the four fields being centralized at the Lacq treatment plant. These fields are now at the end of their life. The last well was drilled at the end of 1990. Since 1957, well pressures have dropped from 70 MPa to as low as 2 MPa. Unstable water production started in the early 1980s on some wells in the Meillon and Saint Faust fields, causing high operating costs because of water-disposal problems. Furthermore, the normally open velocity and ambient valves used on some wells are no longer acceptable because unstable flowing conditions do not allow accurate and repetitive closure. To extend the life of the wells and maximize the recovery factor, Total E&P France has been looking for a solution to replace subsurface-controlled safety valves (SSCSVs) and nonfunctioning SCSSSVs with new SCSSSVs without the need for a work-over. One solution is surfactant injection at the reservoir level. In this case, the challenge is to free the available nipple and set an injection device in the nipple, again without any work-over or wellhead modification. Avoiding WorkoverThere currently are two types of safety systems being used.The SSCSVs are wireline retrievable (WR) and are calibrated well by well according to the latest production conditions. They are less and less compliant with safety regulations.The SCSSSVs are fail-safe production-rate independent, and testable from the surface whether they are tubing retrievable (TR) or WR.

New-Type Energy-Recovering Hydraulic Workover Rig and the Simulation for Lifting the Tubing String

A new-type energy-recovering hydraulic workover rig is researched. The basic structure and working theory of this rig are introduced. This rig decreases its equipped power remarkably compared with the conventional rig, and can recover the potential energy released by the tubing string when lowered. With infinite force-grade number, this rig can obtain the maximum lifting efficiency and energy-recovering rate. The dynamics model of lifting the tubing string is deduced and a simulation analysis is conducted. Through simulation some conclusions are obtained: (1) the greater the throttle valve path area the higher the tubing string lifting velocity, (2) the lighter the tubing string the higher the tubing string lifting velocity, and (3) the greater the displacement of the variable pump motor the higher the tubing string lifting velocity. The actual measurement results prove that the dynamics model and simulation results are basically right.

Technology, investment and people: a process for extending the life of the Central Fields Complex, Gippsland Basin

The greater Central Fields complex of the Gippsland Basin, comprised of the Halibut, Fortescue and Mackerel fields, has produced 1.7 billion barrels of oil from four platforms in 37 years of production. After the initial development drilling phases from Halibut (1969–70), Mackerel (1977–80), Fortescue (1983–86) and Cobia (1983–85) platforms and five in-fill drilling campaigns (1992–2003) it is still possible to target unswept highly productive multi-darcy reservoirs along with bypassed zones in lower quality sands. During 2007, a six well program was completed from the Halibut platform using an upgraded workover rig that added significant volumes with combined initial rates of more than 16,000 barrels of oil per day. In addition, despite being conductor limited, the program tested strategic concepts and demonstrated significant remaining potential in a variety of reservoir qualities and depositional environments. The outstanding success of the 2007 program was based on an up-to-date geologic framework, key technical advances, ongoing investment commitment and multi-discipline integration across workplace functions. Advancements in 3D seismic data quality and analyses, reservoir surveillance, innovative slot recovery and data integration all played a role in the success of the program. Building on the success elements of the 2007 program, a higher capacity rig has been mobilised and upgraded to apply new drilling technologies to access the remaining potential and help mitigate basin decline.

Rigless Interventions in Failed Gravel-Pack Gas Wells Using New Resin Systems

SummaryWhen a gravel-pack completion fails, it usually results in loss of production for the interval until a workover rig is available to recomplete the well. This paper describes two recent successful rigless interventions completed in offshore multizone completed gas wells in the Adriatic Sea. A key factor in the success of these remedial treatments has been the application of two different chemical technologies applied to the proppant while it is being pumped into the well.In the first well, production loss was caused by fines migration (fine silt ≤44 microns) into the 40/60 gravel-pack sand, which completely plugged the screens and gravel. An intervention was performed which included sealing the existing completion and then reperforating the premium screen using wireline guns. The interval was then fractured with a tip screenout design and a through-tubing screen was placed across the perforated screen. Critical to this treatment was the use of a surface modifying agent to prevent fines migration and plugging of the gravel pack. Production results have confirmed the correctness of this technical choice.A different problem existed with the second well, which had a frac-pack completion; in this case, a screen failure resulted in formation sand and proppant being produced to the surface. The well was refractured through the hole in the screen and a newly developed resin was applied to the proppant to lock the proppant into place and thus repair the damaged screen without restricting the flow area with a secondary inner string. Unlike conventional resin-coated proppant at low temperatures, this new type of resin does not require confinement pressure and/or the use of chemical flushes to cause the resin to set. Since the intervention, the well has been producing sand-free at very close to the original productivity index (PI).In both cases, these treatments have put back into production wells that in the past could not have been restored to production except through recompletion using a workover rig. This paper will describe the treatment design, well operations performed, materials used, and production performance of each well, comparing each aspect with the case of a conventional recompleted well.

Ensign Energy Services Inc

AbstractOil and Gas (MIC: 14.2 SIC: 1381 NAIC: 213111)Ensign Energy Services is a public holding company. Co.'s principal business activities include the provision of oilfield services in western Canada, in the Rocky Mountain region and the State of California in the U.S. through Ensign United States Drilling Inc. and Ensign United States Drilling (California) Inc., respectively, and in the international oilfield services market through Ensign Energy Services International Limited (EESI). EESI operates drilling rigs and workover rigs in Australia, New Zealand, Southeast Asia, Middle East, South America and North and South Africa. Co. also provides well servicing, production testing, wireline and oilfield equipment manufacturing services.

True Hybrid Operations Combining Coiled-Tubing Drilling and Conventional Rig Workover Techniques and Practices

Summary This paper documents the results of a new stage of development in the application of coiled-tubing drilling (CTD). Combining CTD technology with a conventional jointed-pipe workover capability represents the next-step change in providing low-cost reserves access solutions through selection of the most efficient tool for the application. Drilling sidetracks using coiled tubing is an established practice in Alaska's North Slope oil fields. During these operations, the use of jointed pipe was avoided, except for running liners, with the CTD rig. A conventional workover rig was the preferred approach to prepare the coiled-tubing candidate well when it required a changeout of production tubing or other workover activity. In 2001, a North Slope operator evaluated the opportunity to utilize one rig to perform both operations. In 2002, a workover rig was modified to fit the need. Integrating two established technologies presented many challenges. Specialized equipment, multidisciplinary personnel, and control of overall well cost are just a few of the many parts of the operation to be planned. This paper details the results, problems encountered, solutions, and a quantification of the real benefits achieved combining CTD with a jointed pipe workover.

Study on Hydraulic Energy-Recovering Workover Rig and the Simulation for Lifting the Pipestring

In this paper, an advanced energy-saving petroleum machinery, the hydraulic energy-recovering workover rig, is researched. The equipped power of this rig is only one third of an ordinary rig, and this rig can also recover and reuse the potential energy which is released by the pipestring when lowered. The special working theory of this rig is introduced. An energy-saving analysis is conducted. Analysis shows that when lowering the pipestring which weighs 260kN, the energy recovered by this rig is about 240×106J. The mathematical model of lifting the pipestring is established and a simulation analysis is conducted. Through simulation, some conclusions are obtained: (1) the lighter the pipestring the shorter the pipestring lifting time; (2) the smaller the throttle valve path area the longer the pipestring lifting time; (3) the smaller the air vessel volume the shorter the pipestring lifting time. The actual measurement results prove that the simulation results are right.

Application of In-Depth Gel Placement for Water and Carbon Dioxide Conformance Control in Carbonate Porous Media

Abstract This paper presents the results of an investigation of the application of gel placement in an attempt to reduce the effective permeability of a carbonate porous medium to water and supercritical carbon dioxide, as encountered in the CO2 flooding of carbonate reservoirs. Three gel systems based on a high and a low molecular weight polyacrylamide polymer with chromium(III), as crosslinker, were used for this study. Since sodium lactate is commonly used for increasing gelation time at elevated temperatures, experiments were conducted by adding sodium lactate to the gel solution with a ratio of polymer to sodium lactate equal to one. The higher molecular weight polyacrylamide gel system was composed of 7,200 ppm Alcoflood 935 and 300 ppm Cr(III), while the other gel system tested was composed of 5% low molecular weight polyacrylamide (Alcoflood 254S) with a ratio of 1:12 chromium(III)-acetate to polymer as crosslinker. Experiments were conducted at 8,274 KPa and 40 °C with and without the presence of residual oil. Performance and stability of the above gel systems for reducing the permeability of the carbonate medium to the injected water and carbon dioxide was tested in a series of flow experiments by alternately injecting several pore volumes of water and carbon dioxide into the porous media in several cycles. The porous medium used was crushed carbonate with an initial permeability of over 9.86 µm2. For all experiments, the presence of Sor led to lower residual resistance factors (RRF). Nevertheless, RRFs were between 100 and a few thousands for all experiments conducted. The results obtained are a clear indication of the effectiveness of these gel systems for conformance control purposes during carbon dioxide flooding projects in carbonate reservoirs. Introduction From the pore-scale point of view, dense carbon dioxide is an ideal displacement fluid for many crude oils. Carbon dioxide gains miscibility with oil and is able to achieve very high recovery efficiencies at reservoir pressures near or above minimum miscibility pressure. However, even when pressure conditions for miscibility are met, this high microscopic sweep efficiency is not often observed in field tests. The combined effect of heterogeneity of the reservoir and the low viscosity of the injected carbon dioxide leads to the viscous fingering of carbon dioxide through fractures, channels, or high-permeable streaks in the reservoir. This causes early breakthrough of injected carbon dioxide into production wells, which reduces oil recovery efficiency. Different techniques have been investigated for reducing channelling through fractures or high-permeability zones. One such technique is in-depth gel placement. This process has been applied successfully in many reservoirs, resulting in fracture sealing, water and gas shut-off, and permeability modification. The objective of gel placement is to reduce fingering of the injected fluid through fractures or high-permeability zones of formation while minimizing gel penetration in hydrocarbon bearing regions of the reservoir. The main advantages of using gels over the other methods, such as cements or mechanical plugs, is their flexibility for pumping without a workover rig, high control of setting time, a deeper penetration into the formation, ease of cleaning, and an easy removal from the wellbore by water recirculation(1, 2).

Ensign Energy Services Inc

AbstractOil and Gas (MIC: 14.2 SIC: 1381 NAIC: 213111)Ensign Energy Services is the public holding company. Co.'s principal business activities include the provision of oilfield services in western Canada, in the Rocky Mountain region and the State of California in the U.S. through Caza Drilling Inc. and Caza Drilling (California) Inc., respectively, and in the international oilfield services market through Oil Drilling & Exploration Limited (ODE). ODE operates drilling rigs and workover rigs in Australia, New Zealand, Southeast Asia, Middle East, South America and North and South Africa. Co. also provides well servicing, production testing, wireline and oilfield equipment manufacturing services.

Scheduling workover rigs for onshore oil production

Many oil wells in Brazilian onshore fields rely on artificial lift methods. Maintenance services such as cleaning, reinstatement, stimulation and others are essential to these wells. These services are performed by workover rigs, which are available on a limited number with respect to the number of wells demanding service. The decision of which workover rig should be sent to perform some maintenance service is based on factors such as the well production, the current location of the workover rig in relation to the demanding well, and the type of service to be performed. The problem of scheduling workover rigs consists in finding the best schedule for the available workover rigs, so as to minimize the production loss associated with the wells awaiting for service. We propose a variable neighborhood search (VNS) heuristic for this problem. Computational results on real-life problems are reported and their economic impacts are evaluated.

Ensign Energy Services Inc.

AbstractOil and Gas (MIC: 14.2 SIC: 1381 NAIC: 213111)Ensign Energy Services is the public holding company. Co.'s principal business activities include the provision of oilfield services in western Canada, in the Rocky Mountain region and the State of California in the U. S. through Caza Drilling Inc. and Caza Drilling (California) Inc., respectively, and in the international oilfield services market through Oil Drilling & Exploration Limited (ODE). ODE operates drilling rigs and workover rigs in Australia, New Zealand, Southeast Asia, Middle East, South America and North and South Africa. Co. also provides well servicing, production testing, wireline and oilfield equipment manufacturing services.

Ensign Resource Service Group Inc.

AbstractOil and Gas (MIC: 14.2 SIC: 381 NAIC: 13111)Ensign Resource Services Group is the public holding company. Co.'s principal business activities include the provision of oilfield services in western Canada, in the Rocky Mountain region and the State of California in the U.S. through Caza Drilling Inc. and Caza Drilling (California) Inc., respectively, and in the international oilfield services market through Oil Drilling & Exploration Limited (ODE). ODE operates drilling rigs and workover rigs in Australia, New Zealand, Southeast Asia, Middle East, South America and North and South Africa. Co. also provides well servicing, production testing, wireline and oilfield equipment manufacturing services.