Advanced Technologies for Exploration and Production of Hydrocarbons

Viktor SavelievViktor Saveliev, Head of Gazprom Neft's Geology and Exploration Directorate, tells about efficiency and innovation in geological exploration and production.

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— What factors, in your opinion, affect the quality of geological surveys?

— The first and most important factor is qualitative selection of areas and locations for carrying out geological and technical programmes. If we’re talking about drilling, then we need a reliable geological model, which is most likely to enable us to determine the reserves in place and their characteristics. I’m talking about the fields which have been deeply explored.

Nowadays practically all Gazprom Neft fields are covered by 3D seismic. Every field has it’s 3D geological and, in most cases, a hydrodynamic model. Hydrodynamic models make it possible to specify a residual reserve zone and place sidetracking at that location, to carry out work to deepen the wells in case any promising horizons are discovered underneath. Regarding hydraulic fracturing (HF), the recompletions to higher- or lower-lying horizons in order to put these well back on stream, the decisive factor in such activities is still the availability of residual reserves profiling and mapping. Although it remains the most effective tool of the present day, 3D models can only be used to their maximum potential if they are constantly updated. Drilling and maintenance work, limiting the inflow of water and changing the injection profile all affect the movement of reserves within the reservoir and change the hydrodynamic model. All of our main fields where geological and technical activity is carried out are covered by sectoral hydrodynamic models in the areas of active work. This has become a standard practice for us, and has enabled us to significantly increase the success of almost all of our geological and technical activities over the last 2-3 years. Nowadays the company’s basic success level does not drop below 85%. If preliminary reports show that we will not reach success at a location, then we simply decline the activities. Another important factor is the Index of Economic Efficiency. Any geological and technical activities should have a profitability index (pi) no less than 1.2; that is to say, we wouldn’t just return our money, we would earn a profit too.

The second factor is the technical execution of work. It’s no secret that a contractor who fulfils all obligations efficiently and with good quality is a very important factor of success. Gazprom Neft applies a strict selection procedure for contractors, including already-qualified applicants. We evaluate how they have worked on our own and other sites, we compare, analyse, carry out a technical audit, check their suitability and potential. Only upon completing this stage does the company begin to participate in a tender. However, even after a contractor is selected and starts work, a positive result is by no means guaranteed. The progress of the work should be continuously monitored. For this, we use a system of internal and external supervision, although both types have their nuances. Internal supervision increases administrative costs, and third-party supervisors should be constantly checked. One or two mistakes is enough to begin a serious analysis of the situation and remove either the supervisor or the contractor.

— Are there any new exploration technologies the company started applying recently? How has their introduction affected the quality of work?

— In Russia, as well as in the whole world, new methods of geological survey appear, at best, once every 20 years. Thus, the main thing is to keep on improving our existing experience. Gazprom Neft has recently been applying complex methods of seismic and electric exploration on new sites. The first method is good for deep study of sites, while the second is indispensable in area survey, providing an opportunity to find zones of low resistivity, which are generally somehow connected to potential hydrocarbon traps. Seismic surveys can help to determine the depth at which these traps are located. Since this method is useful when working at new sites, we will actively use it in Eastern Siberia in the Ignyalinskaya, Tympuchikan and Vakunay areas. As for working on older fields, it is more important to further improve 3D seismic surveying, which recently enabled us to identify not only standard traps, but also nonanticlinal stratigraphic traps, which are being revealed a lot recently. Similar work carried out on the Ety-Pur, Vyngayakha and Vyngapur fields has demonstrated that the company possesses prospective areas for drilling and discovering more reserves. The wells produce good yields of over 100 tons. This makes it possible to build up the resource base and immediately move these reserves into development.

On the new territories, Messoyakha in the north of Yamal and Kuyumba in Eastern Siberia, where we are now carrying out geological exploration, the most important issue is that of efficiently drilling into the producing zones. Contractors today pay little attention to the skin factor, but it shows the potential of the reservoir! We either uncover it, or colmatate the bottomhole formation zone, and as a result of the test we get a marginal flow. Recent years have shown us that a fracture of an exploration well removes the skin factor and gets higher production rates. We understand that this practice requires additional investments, but at the same time it is a key in obtaining high-quality information, on which basis we can continue working for a long time.

These methods make it possible to form a relevant and up-to-date imagery of the fields and, even under the current tax system, to prepare suitable investment projects for their development. If tax incentives are introduced in the Far North regions, we will be able to talk about a significant expansion to our resource base on a nationwide level. The new technologies, together with tax incentives, will make previously unprofitable territory profitable.

— What technical solutions to enhance the oil recovery factor (ORF) are being used by the company? Have company specialists introduced anything new in terms of technology for producing difficult oil?

— We aren’t abandoning the traditional method of water flooding, but we are making significant progress in its improvement. Today it’s no longer only pumping water from an injector into the producing well. We are also applying other methods to increase reservoir pressure: revitalisation of the marginal and aquifer regions and the plantar area of the field. The most important thing during flooding is to control the injection. Currently, hydrodynamic models enable us to move the injection zone to increase production. We aren’t talking about standard regular grids of seven and nine points with clear placement of injecting and producing wells. If the hydrodynamic model shows the presence of zones of residual reserves, we move the injection front there and raise the ORF by 1-3 points.

Not a single well with tight reservoirs is introduced without fracturing. Secondary and tertiary fracturing, carried out three or four years after the production is started at the well, make it possible to work from a remote area of the reservoir to increase coverage and improve the ORF.
The next step in increasing the ORF is the introduction of physical and chemical methods. The injection of surface-active substances (SAS) also makes it possible to manage well development. SAS clog up highly-permeable reservoirs which are mainly moving water, thereby drawing little-drained sites into action. This method is particularly useful on fields at the third and fourth stages of development, and its use adds 2-3 points to the ORF. And if the company has 1 billion tons in recoverable reserves, each point is 100 million tons of oil.

It’s no secret that there are fully-drilled fields out there with remaining reserves. In order to develop them we are applying the methods of sidetracking and multistage hydraulic fracturing. It is currently possible, depending on the length of the bore, to create up to 3-4 fractures and connect several zones of the field. This, again, helps to better manage the development. If one part of the well is full of water, it is covered by a packer and the rest continues to operate. Currently, the company’s approved project documentation provides for an ORF of 0.32, but all of these technologies can increase that up to 0.35-0.37.

— Have company specialists been able to improve the technology for producing difficult oil?

— With the beginning of development of the Messoyakha field, we are confronted with the prospect of developing highly viscous oil. Here, we shall be employing technology to mix this viscous oil with low viscosity oil found in the lower layers, making it possible to prepare the material for transportation. Our specialists often have to deal with oil from low-permeability reservoirs at 1•10—3—2•10—3 um2, and sometimes as low as 1•10—3 um2, as was the case on the southern part of the Priobskoye field. These zones were not previously considered as reservoir rocks, but in 2011 we were able to produce around 11 million tons from our site on Priobskoye. Based on such success, there is no doubt as to the correct application of development technology, including theoretical, mathematical and hydrodynamic calculations. Practice has shown that the most effective system for these reservoirs is row flooding, which makes it possible to tightly regulate screening and management of development and injection. The rate of hard-to-extract oil recovery at Priobskoye has already reached 5-6%, compared with 7-8% at highly-permeable reservoirs. When working on the low-permeability reservoirs of the Noyabrsk zone, the method of deepening wells has proven successful. There are wells drilled in the overlying strata, which are already either depleted or are nearing depletion. However, we knew that beneath them lay more than two dozen potential new traps. Deepening the existing wells enabled us to begin effective development of these reserves, which would have been unprofitable had we been forced to drill new wells.

In Eastern Siberia on Kuyumba and on the Chonsk fields, our specialists are faced with fractured reservoirs, making it necessary to study the direction of the cracks and their potential influence on the development of the reserves. We’re in the process of doing that now, we already have some good examples from our work in the Tomsk region on the Palaeozoic reservoirs of the Urmanskoe and Archinskoe fields. Building up this kind of experience with fractured reservoirs will be very helpful in the future.

Regarding the thermogas method of enhancing oil recovery, I see it as the method of the future. Russia is not yet ready to implement it, because all the necessary equipment, such as compressors, would have to be purchased from overseas. There are no Russian-made compressors that allow you to whip up such a volume of air mass in the reservoir so as to create a displacement front. Gazprom Neft intends to test out this method on experimental plots. The technical documentation is ready, and we plan to present this issue to the Central Commission for Oil Field Development.

We are also starting work at the Achimovskoye fields, which are classified as low-permeability. These reservoirs are characterised by the presence of clay bridges, which means that in the case of massive hydraulic fracturing, there is a danger of breaking through into the underlying reservoir of water. We have selected two sites and will begin pilot operations in 2012. Next year, as a part of our cooperation with Salym Petroleum Development, we will begin to implement a project in the Bazhenov Formation, which is found on our fields in Khanty-Mansiysk. We have already selected a site to drill horizontal wells and apply multistage hydraulic fracturing in order to expand the area for the development of reserves, and based on these results we will take the decision as to whether to use this experience in other areas.