Tatneft: New Technologies to Maintain Reservoir Pressure

ALSU MATISOVA

With many unique oilfields in late stage development, RPM, Reservoir Pressure Maintenance systems, are becoming increasingly important. It is the modern RPM systems, or, more precisely, the new technologies used to maintain the reservoir pressure that make it possible to increase oil recovery.

Tatneft engineers are working first and foremost on the reduction of energy consumption and increasing production efficiency. They are focused on the protection of the downhole equipment in injection wells against high pressure and corrosion, and also on the comprehensive optimisation of the RPM processes.

222 new injection wells were commissioned in 2013, and at 172 of them, dual injection technology has been introduced. Since we implemented this technology, it has been used in 581 wells, which have provided an incremental production of 1146.5 thousand tons of oil.

RPM SYSTEM MILESTONES

The evolution of the RPM system at Tatneft can be split into five stages. It stems from the USSR Council of Ministers Decree dated 28 April 1959, when it was decided to design a peripheral water flooding system at Romashkinskoye and Bavlinskoye fields in order to increase oil production. It was there where the construction of the first water treatment and injection facilities started, where injection wells were commissioned, cluster pumping stations and the associated high pressure and low pressure water pipelines were built.

During the first stage, from the late 1950s to 1985, the RPM system was formed and began to quickly develop. This was encouraged by large amounts of oil production and the associated large volumes of water injection. During the second stage (1985-1995), the main task for the specialists was to solve the problem of the reliability of the system’s water pipelines. Pipes with anti-corrosive coating were barely in existence then, and corrosion protection technologies were not widely used in oil production. Because of this, we would say the key feature of this stage was a catastrophic increase in the number of water line ruptures (more than 20 ruptures a day) and the reduction (splitting) of the remaining oil reserves and the produced and injected water volumes.

The decisive factor in the improvement in reliability of the water pipelines was, of course, using pipes with internal and external protection coatings. The large-scale introduction of steel-plastic pipes (SPP) reduced the failure rate by a factor of 30. During the next, third stage (1995-2002), Tatneft engineers specialising in RPM began to upgrade the RPM pumping stations and establish the conditions for a more targeted injection. Science was moving forward and some brand new technologies were being developed that would provide the stability of the RPM system. During that period such tools as low flowrate pumps emerged, a wide range of high-quality downhole and cluster pumping station equipment and clamp-on flowmeters was in use.

During the fourth stage (2003-2010), the company aimed to achieve comprehensive optimisation of the RPM processes, mainly using software packages. The programme for replacement of conventional tubing strings in injection wells with polymer-coated tubing strings was actively implemented.

The fifth and current stage is expected to end in 2015 and is aimed at injection targeting, increasing the reliability of the pumping units, downhole equipment and pipelines, energy efficiency of the RPM system at large. This stage cannot be called the last stage, as the RPM system is constantly evolving.

For the period ending 2015, a tailored “RPM System Reconstruction and Development Concept” was adopted. Its key feature is the integration of applying the new engineering and process solutions. This would help the company achieve the maximum oil recovery factor while optimising energy consumption.

AIMING AT ENERGY EFFICIENCY

It is no secret that the RPM systems at oilfields are characterised by high energy consumption. They demand more than 30% of the electric power consumed by the company. The pumps at the cluster pumping stations are the most power intensive units. These days, the company specialists are trying to reduce their energy intensity.

To this effect, every year the company, together with OOO “UK Sistema-Servis”, the company that services these pumping units, establishes a programme for major repairs and optimisation of the pumping units. This programme, based on the feasibility study calculations, makes it possible to carry out major repairs of the pumping unit when necessary, thus saving the company approximately 28.8 million roubles a year.

Tatneft pursues the objective of energy saving by having started the pilot operation of two displacement pumps manufactured by German companies KAMAT (in NGDU “Almetyevneft”) and WEPUKO (at NGDU “Elkhovneft”). The results of the 2013 pilot operation demonstrated that the energy intensity of these pumps is 2-2.5 times lower than that of centrifugal pumps having similar characteristics. That’s why the company decided to purchase five more pumps: two KAMAT pumps (for NGDU “Almetyevneft”) and three WEPUKO pumps (two for NGDU “Elkhovneft” and one for NGDU “Leninogorskneft”). Their maintenance is carried out by the specialists of OOO “UK Sistema-Servis”.

At present, most of the RPM system equipment (pumping units, auxiliary equipment of the cluster pumping stations), downhole and wellhead equipment (tubing, packers, injection valves) is serviced by the specialists of two Tatarstan service companies, OOO “UK Sistema-Servis” and UK OOO “TMS Group”, under the contracts executed between them and OAO “Tatneft”. The centralisation of service in managing companies enabled the optimisation of the equipment stock and the costs of its maintenance, organisation of circulating equipment stock, and reduction of the downtime caused by its repairs.

INTELLIGENCE IS THE FUTURE

Intelligence rules the world. The production industry cannot evolve without science. The efficiency of cooperation between science and production industry is evidenced by the long-term joint work efforts of the scientists and oilfield personnel. The production and scientific potential of Tatneft is closely associated with the activity of TatNIPIneft.

The institute, established in 1956, is one of the largest scientific centres within the oil industry. Petroleum scientists are now solving the most complex scientific and engineering design problems related to the integrated development of oil fields in various mining and geological environments. The RPM system has not been neglected by them either. Nowadays, Tatneft successfully implements a technology developed by TatNIPIneft specialists – the technology of disposal and treatment of produced water at a well clusters. The purpose of the technology is the separation and treatment of the produced water at a well cluster followed by its injection into injection wells of the same cluster.

Pilot testing was conducted at a unit installed on the well cluster at GZU-50A (pad metering station) of CDNG-4 (oil and gas production department) of the Arkhangelskoye field being developed by NGDU “Yamashneft”, as division of OAO “Tatneft”.

The key factors contributing to the success of the project were smaller volumes of fresh water used for RPM; a reduction in the energy consumption required to pump fresh water, produced fluids and waste water.

The new design solution allows a reduction in the volume of liquid transferred by oil gathering and RPM system lines and the consumption volume of fresh water injected into the formation. The technology allows a reduction in the diameters of oil pipelines and water pipelines, which results in lower capital costs during construction. This “frees up” the initial water separation units and oil processing units, which allows a reduction in the capital costs of their upgrade. It effectively reduces the cost of oil processing. This is indeed energy efficiency in practice!

Naturally, it’s not a one-off solution. Among successfully implemented TatNIPIneft’s technologies are the dual injection that enables injection into two or more reservoirs from one well, thus saving on the costs of drilling a new well; inter-well and intra-well pumping, which makes it possible to inject reservoir fluid and either recover it at the surface or not, and a great many other engineering solutions and technologies aimed at the improvement of the RPM system management.

The company fine-tunes its new technologies at the so-called Digital Oil Fields. Automation facilities, when developing “difficult” oil reservoirs, provide the oil workers with an opportunity to optimise their equipment capacity and well productivity by analysing their data, and also to forecast the well depletion dates based on historical data. At the same time, the data relating to the older production wells can be used to forecast the behaviour of new wells. Advanced automation systems allow us to centrally control a large number of wells using remote monitoring systems.

Intellectual elements are also introduced to the RPM system. In NGDU “Almetyevneft”, at the third block of the Berezovskaya area, a pilot project has been implemented to use the software package that controls the inter-well pumping system (IWP). This programme allows us to obtain the data on the operation of the electric submersible pumps in the inter-well pumping system, to process the obtained values, identify deviations of actual values from the setpoint (operational) ones, and to produce such deviations in the form of reports. The program provides integration of operating parameters of injection and production wells, and generates recommendations on the changing of the injection mode.

Among leading-edge technologies for flooding in the late stage of field development are those that allow us to maintain the targetted oil production level for mature fields. In addition to the above mentioned dual injection, intra-well pumping and inter-well pumping, there is the injection of various chemicals for enhanced oil recovery (EOR) using mobile KUDR units (a fleet of mobile units for batching and injection of bulk and liquid chemicals into wells to enhance oil recovery). Injection into injection wells is carried out in order to straighten the injectivity profile, deflect the flow and increase the injectivity.

Special engineering designs are also used in the fields that are located at large distances from water sources. In such fields, individual electric submersible pump systems or inter-well / inter-well pumping systems are used, which help organise targeted injection for RPM.  For the optimum implementation of the established injection mode, a standard-size electric submersible pump is selected.

When discussing advanced technologies we should of course take note on environmental protection. As an example, using the system of corrosion-protected water pipelines allowed us to cut down the number of ruptures of waste water pipelines in the RPM system by a factor of more than 30. Using protected PE-coated tubing strings and extremely leak-tight M1-X packers allows us to efficiently protect the production strings of injection wells from high pressure and corrosive waste water, which, in turn, not only cuts the well servicing costs but also reduces the negative impact on fresh water aquifers and preserves water springs.

Ultimately, all the efforts of RPM specialists are aimed at searching for efficient solutions to further improve development conditions and resource-saving.

There will always be more new ways to reduce energy consumption and we must not be complacent. It means that the introduction of new engineering solutions and technologies will continue in the future.