Yukos Oil Company is the second largest oil production company in Russia, and produces 1.2 million barrels daily, with > 60% of this coming from fields in W. Siberia. Base oil and gas production units are located in the European part of Russia (OAO Samaraneftegaz) and W. Siberia (OAO Yuganskneftegaz and OAO Tomskneft VNK) [1]. This production comes from a variety of fields, and it is common for these fields to produce at significant water cuts. Produced water leads to several production and cleanup problems (since it is also re-injected), one of these being the problem of mineral scale. The most common scale is calcium carbonate and this is found in both mild and more severe scaling cases. Sulfate deposits are present too in minimal amounts. However, a feature of the W. Siberian reservoirs is that they have many thousands of wells. Therefore, although the technical problem of treating a single well may not be large, the approach and logistics to protect such a large number of wells is a significant challenge. In this paper we survey the problems of scale in these W. Siberian fields and we outline how Yukos has approached this challenge. Introduction Two production units, OAO Tomskneft and OAO Yuganskneftegaz, carry out the main oil production in Western Siberia on the territory where Yukos has licenses. Fig.1 shows the geographical placement of Yukos's main production and refining units. A brief description of them is presented below. OAO Tomskneft VNK. OAO Tomskneft VNK is the principal Production Association of Yukos subsidiary OAO "Vostochnaya nefteyanaya kompanya", also known as VNK or the Eastern Oil Company. Established in 1966, Tomskneft VNK has produced more than 2 billion barrels of oil since it began its operations. 21 fields are currently under development or in production. Tomskneft VNK operates in the remote western part of the Tomsk Region in Western Siberia. Some of its more unusual assets include its own fleet of river barges and approximately 1,000 kilometers of service roads. Since over 70% of its recoverable reserves fall into the "difficult recovery" category, Tomskneft VNK has introduced advanced technologies for horizontal drilling and deep hydraulic fracturing of formations. It has also begun to acquire additional licenses for the development of several new areas in the Tomsk Region. At present there are 1880 production and 840 injection wells in operation. The average oil rate is 170 bbl/day, and the average water cut is 65%. OAO Yuganskneftegaz. OAO Yuganskneftegaz is the Yukos Oil Company's largest Production Association - and the second largest in all of Russia. Yuganskneftegaz, located in the Khanty-Mansi Autonomous Area of Western Siberia, first began operations in 1964, and has produced over 9 billion barrels of crude to date. At present, Yuganskneftegaz manages 29 fields, the largest of these being Priobskoye, Prirazlomnoye, Mamontovskoye, Malo-Balykskoye and Salymskoye. The Priobskoye field is unique as to its geological structure. Recoverable reserves are estimated at 3.01 billion barrels. Prirazlomnoye has 2 billion barrels reserves; a three-dimensional seismic survey of the field has revealed the existence of promising areas that could significantly increase production there. In order to improve well operation, Yuganskneftegaz is introducing hydraulic fracturing and implementing a program to increase efficiency and reliability at its production sites. The program includes improving the power supply system, purchasing additional up-to-date well equipment, and establishing a network of production supervisors. At present there are 6000 production and 2300 injection wells in operation. The average oil rate is 169 bbl/day, and the average water cut is 71%. OAO Tomskneft VNK. OAO Tomskneft VNK is the principal Production Association of Yukos subsidiary OAO "Vostochnaya nefteyanaya kompanya", also known as VNK or the Eastern Oil Company. Established in 1966, Tomskneft VNK has produced more than 2 billion barrels of oil since it began its operations. 21 fields are currently under development or in production. Tomskneft VNK operates in the remote western part of the Tomsk Region in Western Siberia. Some of its more unusual assets include its own fleet of river barges and approximately 1,000 kilometers of service roads. Since over 70% of its recoverable reserves fall into the "difficult recovery" category, Tomskneft VNK has introduced advanced technologies for horizontal drilling and deep hydraulic fracturing of formations. It has also begun to acquire additional licenses for the development of several new areas in the Tomsk Region. At present there are 1880 production and 840 injection wells in operation. The average oil rate is 170 bbl/day, and the average water cut is 65%. OAO Yuganskneftegaz. OAO Yuganskneftegaz is the Yukos Oil Company's largest Production Association - and the second largest in all of Russia. Yuganskneftegaz, located in the Khanty-Mansi Autonomous Area of Western Siberia, first began operations in 1964, and has produced over 9 billion barrels of crude to date. At present, Yuganskneftegaz manages 29 fields, the largest of these being Priobskoye, Prirazlomnoye, Mamontovskoye, Malo-Balykskoye and Salymskoye. The Priobskoye field is unique as to its geological structure. Recoverable reserves are estimated at 3.01 billion barrels. Prirazlomnoye has 2 billion barrels reserves; a three-dimensional seismic survey of the field has revealed the existence of promising areas that could significantly increase production there. In order to improve well operation, Yuganskneftegaz is introducing hydraulic fracturing and implementing a program to increase efficiency and reliability at its production sites. The program includes improving the power supply system, purchasing additional up-to-date well equipment, and establishing a network of production supervisors. At present there are 6000 production and 2300 injection wells in operation. The average oil rate is 169 bbl/day, and the average water cut is 71%.
Rosneft has oil fields in Western Siberia producing fluids from a number of wells via Electric Submersible Pumps (ESP's). While production rates are increased using ESP's, run time can be compromised by the formation of scale within the inner workings of the pump. The deposition of scale can be detected by the pumps requiring increasing amounts of current to maintain the flow rates. Eventually the pumps fail (either mechanically or electrically) and have to be replaced. Typically examination of these pumps indicated the main failure mechanism to be the deposition of Calcium Carbonate scale within the pump. The actual run times achieved tend to be dependant on the severity of the scaling produced water, but were typically in the order of weeks. However in some extreme cases, pump failures had occurred in a matter of days from replacement and start up. It was proposed that one treatment strategy to increase the pump run time by inhibiting scale formation was via a Scale Inhibitor Squeeze application treatment. The Squeeze process and inhibitor application is very well understood, but to get successful squeeze treatment you need to perform adequate laboratory selection tests, including inhibition efficiency testing and core flood evaluations. This data, together with the Heriot Watt University Squeeze VI modeling can get an approximation to the potential squeeze life. This paper presents the testwork performed to identify and develop successful Scale Inhibitor Squeeze Chemistries suitable for application in Western Siberia. It details the laboratory testing, the coreflood evaluation and Squeeze VI modeling. The Squeeze application and performance of the first well squeezed is reviewed together with a summary of the current status of the wells squeezed. An economic evaluation of the squeeze is also performed together with a summary of all the wells treated which demonstrates that the squeeze application provided a very cost effective method of scale control to maximize pump run time and increase the net well value. Introduction Yuganskneftegaz is Rosneft's largest oil-producing enterprise. It holds licenses to develop 26 oilfields located in the Khanty-Mansiysk Autonomous District of Western Siberia. Yuganskneftegaz was established in 1977, and in early 2005, it was fully integrated into Rosneft's core production base. Yuganskneftegaz is responsible for fields that contain approximately 16% of Western Siberia's recoverable oil reserves. Nearly 80% of them are concentrated in the Priobskoye, Mamontovskoye, Malobalykskoye and Prirazlomnoye fields. Production of oil and associated gas at Yuganskneftegaz in 2006 amounted to 56 million tonnes, and 1.5 billion cubic meters, respectively, which is 70.1% and 11% of Rosneft's total production. Yuganskneftygaz Primary fields are: Priobskoye, Prirazlomnoye, Mamontovskoye, Malobalykskoye The number of wells in production in 2006 was 7,707. The average production per well is 21.3 t/day (2006).
At the present time, the YUKOS Oil Company is applying various techniques to maximize oil recovery. Some of these techniques, such as waterflooding, are leading to an increase in the number of wells that face scaling problems. Various technologies are being used for scale management in these wells, including, for example, continuous inhibitor dosing utilising surface dosing systems. This method has some disadvantages, including the high cost of the service. In addition, this technology only protects downhole equipment from damage by scale deposits, but the bottomhole formation zone remains unprotected. Some years ago we recommended that production wells be protected via scale inhibitor application in the injection waters used for reservoir pressure control and sweep. Experiments conducted have shown that this technique may be used for certain production well types with scaling problems when these are located in relatively close proximity to their supporting injection wells. This paper presents the experimental and field results when this technique was tested in the South-Surgut oilfield. Before testing, a preliminary investigation of the formation geology and hydrodynamic connectivity between injection and production wells was carried out. Next, a large number of experiments were carried out to select an efficient inhibitor chemistry, to test for inhibitor adsorption on the reservoir rock, to evaluate an initial MIC for the solution, and to determine the inhibitor dosing periodicity. During testing of this technique, the inhibitor concentration in the produced water was regularly measured, and the impact on protection against scale was continuously evaluated. It was demonstrated that the inhibitor concentration in the produced water did not decrease below 5–10 ppm on average during 150–200 days for all wells. As a result, the interval between workovers for pump equipment increased by approximately 2.5 times. Furthermore, oil production was increased relative to the period before introduction of this technology. An economic evaluation was carried out that showed the viability of using this technology for the protection of wells in a compact injector-producer pattern. Introduction Due to application of various techniques to maximize oil recovery in Yukos oilfields, the number of wells with scale problems is increasing. As the results of analysis of deposits on ESP wheels shows [1], the portion of inorganic deposits which is soluble in hydrochloric acid amounts to 99.8 % [2]. In addition, it should be mentioned that the content of the iron oxides and hydroxides are low in comparison with calcite and magnesium carbonate deposits. As is well known, the main reasons for the formation of carbonate deposits are pressure and temperature changes during oil production [3–6]. These may lead to decreasing carbonic acid content in the produced fluid and, as a consequence, to carbonate scale depostion on downhole equipment:Equation 1 The main scale prevention methods in Western Siberian oilfields are as follows [7]:A continuous dosing either topside or downhole.A periodical inhibitor dosing at the well bottom hole.Inhibitor treatment application via pressure support water injection wells. For scale prevention the continuous inhibitor dosing utilising surface dosing systems is widely used [3]. In spite of its efficiency, this technology has disadvantages, such as high costs for dosing and system maintenance. An alternative to this technology is inhibitor dosing into the injection system. The first experiments using this alternative technology were carried out in Bashkortostan, but without detailed analysis of the results. Yukos Oil Company is interested in trying this new method elsewhere, and the South-Surgut oilfield (Khanty-Mansi Autonomous Area) was selected for testing.
The deposition of inorganic substances that accumulate in the Electric Submersible Pumps (ESP′s), tubing, and piping systems, equipment for the collection of oil is a significant complicating factor in oil production. The practical results of scale management was shows that the cost of prevention scale deposition is ten times less than the financial cost to remedy the effects of scaling. This paper presents the main provisions of the technical and economic management strategy scaling in the West Siberian oil fields Rosneft, are the criteria for selecting technologies to prevent scaling, implemented in the form of matrices and patterns, as applicable, developed an integrated approach based on the identification of “bottlenecks” in the full cycle of oil production: from the producing formation to the processes of the oil. Depending on the degree of salt saturation of formation water, oil sold technology, offers a range of technologies to combat scaling - from simple, traditional methods of protection to more complex integrated treatments. It is shown that the implementation of such an approach leads to a significant reduction in costs due to the problem of scaling.
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