No.4, 2005

LUKOIL-Western Siberia keeps up-to-date with progress in oil production technology

Oil fields of Western Siberia have been producing oil and gas for more than 40 years. With the passage of time, that gigantic "mature" oil-bearing region's hydrocarbon resources pattern is deteriorating; therefore the maintenance of a steadily high production level requires the use of advanced technologies. LUKOIL leads the oil industry in gearing the latest of what technological progress brings in its line of business towards lower production costs and higher oil recovery efficiency on Siberian fields.

Meeting new challenges

The time when the Soviet leadership's injunction "to keep oil production high at all costs" was a guide to action for oilmen is long past. Notably, the former accelerated rates of oil production were largely to blame for a sharp production slump in the region in the early 1990s.

Today, oil companies are after enhancing production efficiency rather than rushing production rates to record highs. In a region as vast as Western Siberia taking up an area of about 3 million km² the likelihood of discovering new hydrocarbon fields remains quite high. However, it is only a revolutionary approach to the development of "mature" fields that makes for a confident improvement in the performance of the oil companies operating in the region, LUKOIL above all. Until very recently, the so-called low-density oil obtained at high flow rates and low production costs has been produced in Western Siberia. Now, there have arisen difficulties connected with hydrocarbon production at late stages of field development - specifically, a high level of water encroachment, the presence of various salts and resinous paraffin formations. The structure of Western Siberia's crude oil reserves is extremely complicated, with about 60% of the local oil fields running low. This trend characterized by a rising level of well stream watering and a decrease in well production rate is becoming ever more strongly pronounced.

In the total amount of commercial oil reserves which are controlled by LUKOIL-Western Siberia, strata of Group B (33%), A₁ (22%) and J₁ (19%) account for 74%, and other categories, for a mere 26%. In the pattern of C₂ Category reserves, the share of the most productive and actively recovered Group B strata is diminishing.

The most active part of the holding company's resources is largely depleted and watery. Newly-discovered fields are less productive. Now LUKOIL-Western Siberia concentrates on keeping oil production at the high level achieved to date (over 52 million tons). This can be succeeded through raising production efficiency at both early and late stages of oil field development.

In accordance with the modern theory of field development, enhanced oil recovery (EOR) methods are to be used when extracting hard-to-recover reserves and post-flooding residues. Therefore, large-scale employment of EOR methods in fields under development is often put off till the moment when water-flooding potential has been exhausted. On the other hand, the development of even readily-recoverable reserves through reservoir water-flooding is impossible without using elaborate production stimulation and enhanced oil recovery techniques at all development stages. By now, LUKOIL-Western Siberia has developed and field-tested a broad range of hydrodynamic, physical and physical-chemical methods of treating beds of various types with a view to further improving field development systems.

Intensification is the key link

The water-flooding technique pioneered by Russian oilmen in the Volga area in the 1950s has found an extensive application in Siberian fields as well. It is noteworthy that about 50% of the oil produced by LUKOIL-Western Siberia comes from hydrocarbon fields in their third and fourth development stages.

Oilmen know from practical experience that the first stage of oilfield development using water-flooding technology is marked by a steady increase in oil production caused by scheduled field drillout, in-fill drilling and formation pressure maintenance measures. Stage two is characterized by peak production, accompanied by water-flooding system improvement. Stage three is characterized, as a rule, by a decline in oil production due to water ingress into wells. Under maximum flooding conditions (say, 98%) the further field development strategy may follow two scenarios. The first one consists in plugging flooded wells and reducing water pumping rates which leads to the destruction of the established reservoir pressure maintenance system, a rapid decline in oil production and makes it impossible to achieve the planned oil recovery factor (ORF) in the foreseeable future. Our company prefers the second scenario - the use of a set of special water cut reduction methods. The last, fourth, stage provides for recovering the available reserves by means of the flooding method. The classical examples of late-stage development involve fields containing no more than 20% of residual recoverable reserves at the initial recoverable reserves withdrawal rate of under 2% and a water encroachment level of over 90%. Profitability of operations carried out at this stage depends heavily on market price fluctuations. The structure of the residual reserves of such oil fields is to be ascertained then by all-round geophysical, seismic and other surveys.

The idea of using special EOR methods at the first stage is to achieve rated well production conditions and to intensify recovery. In this connection, much higher standards are set for pay bed primary and secondary penetration efficiency, well construction quality, for the thoroughness of reservoir segregation and well cementing reliability.

By implementing the provisions of the Comprehensive Program for Field Development and Oil Production Optimization LUKOIL-Western Siberia has gone a long way toward the solution of these problems. Our company's personnel have carried out a broad range of R&D projects aimed at improving the quality and updating the technology of well construction drawing upon advanced technologies developed by Russian and foreign oil companies. The quality of primary reservoir penetration has been markedly improved through using polymer drilling muds of the Poroflok and Polycarb types and biopolymer drilling muds which leave the properties of the reservoir being penetrated practically intact. Drilling muds developed by LUKOIL's KogalymNIPIneft R&D Institute have improved pay bed drilling-in quality 2.8-3 times while being an order of magnitude cheaper than their foreign analogues. This means higher well construction quality at minimum cost.

At the first field development stage, well flow rate is increased by a variety of influx and well injectivity intensification methods other than conventional acid formation treatment such as small-scale hydrofrac to draw fluid from the undamaged part of the formation to the well, wave treatment of wells for the purpose of bottom-hole zone cleaning, second borehole and horizontal well drilling, bottom hole treatment using original chemical compounds based on surfactants, solvents, emulsions, etc. Taken at the initial field development stage, these measures cut the time required to achieve top production 10-15%.

At the second stage, the priority is to set up a flooding and formation pressure maintenance system that practically eliminates non-drained zones throughout the field and maximizes the stability of oil displacement fronts. This is of special importance for reservoirs in which several pay beds have been merged into one through injecting or producing oil-well systems.

The drilling of in-fill wells involves a certain amount of risk owing to the disturbance of the original reserves structure by piled-up samplings and water injection. Heterogeneity causes fluids to take unpredictable routes. It has always been standard practice, however, for design documents to set uniform well patterns non-adapted to geological bodies and their dynamic parameters as regards area and profile. As a result, flooding systems often turn out to be ineffective, wells get prematurely shut in, and subsequent attempts at rectifying the situation by in-filling the well stock are not always successful.

The later the well pattern is optimized, the less effect optimization has on field producing capacity. Consideration must be given to the fact that current oil saturation is a continuously deteriorating value and that the time factor has the decisive influence under the circumstances both on the rate of recovery and on oil recovery efficiency. It is for that very reason that LUKOIL-Western Siberia's specialists seek to prevent delays in well pattern optimization.

The holding company has worked out, expressly for that development stage, special techniques of forced fluid withdrawal, cyclic water injection, in-fill horizontal and multi-hole well drilling and large-scale hydrofracs. An extensive use of EOR methods permits our company to prolong the maximum field productivity period by an average of 15-25%.

Most of the West Siberian holding company's fields are suffering a decline in production, therefore the strategy of using EOR methods in the final development stage is of paramount importance for the company. In the final analysis, efforts to combat wellstream watering prolong "oil field life" and help achieve rated production indices. The chief means toward that end are an extensive use of stream deviation technologies in injection wells and new methods and techniques of water encroachment rate control in producing wells (bottom hole treatment, repair and insulating operations, etc.)

The company attaches great importance to creating geological-hydrodynamic reservoir models and modifying them in the process of field development. Modern Russian and foreign software complexes are used for the purpose. The models make it possible to locate the main low-drained zones of the reservoir, to ascertain technological and economic efficiency and practicability of various EOR and project options. Realistic geological-hydrodynamic models of commercial fields make for highly efficient oil production.

Translating theory into practice

An all-out realization of this concept at all field development stages enables LUKOIL-Western Siberia to solve the problem of oil production stabilization and accounts for about 30% of the company's output.

The late stage of field development naturally involves its own sets of specific technological issues of objective and subjective nature. The first one arise from geological and natural factors, and the subjective ones have been created by man over the preceding period. They can be explained by "deviations from the chosen project solutions" no matter how good or bad the project is. Notably, projects - major ones, in particular - are to be carried out in 1.5-3 years. Over that period, decisions made at the conceptual stage cease to apply owing to the dynamic nature of the oil field development process. A monitoring system is set up to become part of the oil production process not as an alternative to the project but as a means of expediting decision-making. It keeps track of on-site situations and helps work out optimum development tactics. Close interaction between production and research divisions has the leading role to play here.

As the hi-tech equipment used becomes increasingly sophisticated, ever-higher standards are set for the competence of LUKOIL-Western Siberia's personnel, and cooperation with research organizations gains in importance. The KogalymNIPIneft Institute has started a branch facility in Tyumen in December 2004 as part of its R&D plant expansion scheme. Besides, the company cooperates with Tyumen State University, I.M.Gubkin Russian State University of Oil and Gas and Ufa State Oil Institute, in developing frontier technologies and in training new generations of top-skilled oil industry specialists.

The company keeps close watch on the worldwide practice of residual oil recovery in the United States and China, above all. In our opinion, government support for overall reservoir stimulation projects (not restricted to bottom-hole zones) aimed at winning residual oil reserves is an important factor in ensuring oil production stability. The record of a highly rewarding use made in that country of air-gas, polymer, surfactant-alkaline and other flooding methods indicates the possibility of bringing the ultimate oil recovery factor up to 60-75%. Our specialists analyze the key factors behind the rapid progress of China's oil industry - such as on-going field research into large-scale oil recovery enhancement methods. The results of field tests of microbiological and physical-chemical reservoir simulation methods, carried out abroad, are also of tremendous interest to us.

It should be noted, in conclusion, that despite their "mature age", Western Siberian oil fields are showing a continuous increase in proved reserves. The world's leading analysts predict that toward the year 2012, Western Siberia may boost oil production to 10 million barrels a day and keep it up at that rate for at least a decade. As far as LUKOIL is concerned, its corporate strategy provides for an annual 2-3-percent increase of oil production in this region. An efficient use of the latest technologies and highly productive equipment makes us confident that our company will keep up oil production in Western Siberia at a high level for decades to come.