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June 29, 2007
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Home / Issue Archive / 2007 / May #5 / Problems of Natural Bitumen Production from Formations Having Strong Skeleton

№ 5 (May 2007)

Problems of Natural Bitumen Production from Formations Having Strong Skeleton

According to estimates of Western specialists, total world geological reserves of natural bitumen amount to approximately 260 billion tons, 70 billion tons of which are considered to be recoverable.

 

By B.M. Kurochkin, D.F Baldenko

Bitumen production is considered to be the main strategic potential in hydrocarbon production in Russia in the near future [1]. According to data of the Institute of Geology and Production of Combustible Minerals, natural bitumen (NB) occurs in the Permian formations of the Volga-Ural province in Russia and is concentrated in sandy organogenous clastic rocks. Today NB production is a difficult and expensive method of hydrocarbon production. 

At present, the maximum economic effect is achieved only when NB deposits are developed by the so-called open-cut method. Application of this method is limited to a depth of 30-50 m. For NB at other depths, mine and well technologies are utilized using the application of thermal-gravitational methods, which enable rather limited production. Thus, development of new technologies for NB production from deeper intervals became an urgent problem. At the first stage a solution could be related to production of loose, unconsolidated natural bitumen which is performed utilizing water jet devices with nozzles, through which drilling fluid/heat carrier (water, solution, resin vapor) is circulated. In this method, after rock destruction, slurry containing NB is transported through the usep of ejectors [2].


When this method is utilized at depths exceeding 100 m, it becomes necessary to utilize submersible pumps in addition to ejectors in order to ensure lifting of the bitumen pulp to the surface.


However great difficulties arise during NB production from permeable formations with a strong structure which cannot be destroyed by utilizing ejectors.
Taking into account the importance of the problem of NB production from formations with a strong rock skeleton, VNIIBT (All-Russian Research Institute of Drilling Technologies) is developing a new technology in which a cellular production system is formed which passes through the whole reservoir and ensures the communication of all channels with the major accumulating one. The cellular system needs to be periodically cleaned with the help of a special device (Fig. 1).


In our opinion, the application of electrodilling methods for the directional drilling of numerous holes in order to form a cellular system in a reservoir containing bitumen (monitored utilizing a perfect telemetry system) is the best solution for the given technological task. Power supply of the submersible pump can be provided by the cable connected to the electrical drill.


This combination provides a new drilling technology not only for common directional wells, but also for horizontal branched wells. This technology makes it possible to keep drilling at the lowest differential pressure against penetrated pay beds with complete control of the borehole trajectory utilizing a telemetry system run on electric cable.


New electrical drill designs, for example designs of valve electrical drills of RITEK [3], allow the possibility of implementing the technology for well drilling with reverse circulation utilizing one or two screw pumps installed in the drill string. One of these pumps is installed close to the bottomhole with the electrical drill (Fig.2).


Modern submersible valve electric motors make it possible to utilize single-screw pumps in a regulated mode, varying the liquid delivery as technical necessity requires. Single-screw pumps of such type can have adjustable drives, making it possible to change the pump delivery in order to control and regulate fluid level in the annulus during underbalanced drilling.


It is quite practical to use single-screw pumps with the technology under discussion as the latest versions of these units are characterized not only by high wear-resistance, but also by thermal stability up to 150-1,600 С [4].
Developed technological systems for utilization of electrical drills in combination with submersible pumps for viscous oil and bitumen ensure underbalanced drilling with reversed circulation, enabling preservation of reservoir productivity [6].


In this connection, NPO Burovaya Tekhnika - VNIIBT proposed a method for development of bitumen deposits and bitumen production on the basis of multilateral holes located at certain distances from one another. These holes are drilled with an electrical drill and submersible electric screw pump with reverse circulation of drilling fluid/heat carrier (saline hot water or steam) for heating the bottomhole zone and production of "warmed-up" bitumen. The drilling fluid/heat carrier is delivered by a small-diameter string installed along or inside the drilling string [2].


It is possible to produce bitumen from carbonate formations utilizing a dual-string design (Fig.3). According to this method, the drilling fluid/heat carrier is delivered through the annular space.


In such a situation it is possible to realize the presented method by drilling a lateral hole from the 245-mm casing. Diameters of the electrical drill and screw pump make it possible to have a channel of sufficient diameter along the whole drilling assembly, along which it is possible to lift bitumen slurry to the surface.
After the system of open holes is formed in the productive stratum it is possible to re-enter these open holes one after another to achieve continuous bitumen production.


Sequential production of bitumen from the system of holes with simultaneous drilling of new ones enables production at minimal expense as bitumen accumulates in the holes during the cyclic round. For bitumen production from a certain area, it is necessary to provide a stationary unit for heat carrier supply and drilling assembly including an electrical drill. All this forms a basis for a system of continuous bitumen production with minimal heat carrier consumption.
If sufficient investment is provided for these projects, the proposed methods can find wide application in the oil and gas industry.

REFERENCES


1. R.Kh. Muslimov, V.G Golyshkin, R.M. Yangurazov et al.  Experience of Horizontal Hole Drilling in Natural Bitumen Deposits. Scientific and technical journal "Interval", No 2, 2002.
2. B.M. Kurochkin. Technology of Natural Bitumen Production by Thermo-Gravitational Method. Drilling and Oil. No 2, 2007.
3. V.I. Pavlenko, M.L. Ginzbug.  Justification of the Control Range for Rotational Speed of Drives on the Basis of Valve Electric Motors.  Technologies of Fuel and Energy Sector, October, 2006.
4. D.F. Baldenko, F.D. Baldenko, A.N. Gnoevykh. Single-Screw Hydraulic Machines.  V.1 Information Abstract Digest, Gazprom, 2005.
5. B.M. Kurochkin, D.F. Baldenko. Method for Natural Bitumen Production. Application for an alleged invention No. 2006142229 of 30.11.06
6. B.M. Kurochkin, D.F. Baldenko, V.I. Pavlenko, N.L. Prusova, O.K. Rogachev. Device for Underbalanced Drilling with Reverse Circulation. Application for an alleged invention No. 2007107672 of 01.03.07.

• Boris Kurochkin heads a laboratory which specializes in new methods and tools which prevent well troubles at the Burovaya Tekhnika Scientific and Production Association; Candidate of Science (Engineering); Honored Inventor of the Russian Federation; ([email protected]).

• Dmitry Baldenko is a chief research engineer at the Burovaya Tekhnika Scientific and Production Association; Doctor of Science (Engineering); Academician of Russian Academy of Natural Sciences; Honored Inventor of the Russian Federation;  ([email protected]).

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