NOVIKOV Y.N., GAZHULA S.V.
VNIGRI, Russia

“The classification of reserves and forecast resources of oil and combustible gases”, which establishes uniform principles of the classification of oil and combustible gases reserves and resources for the Russian Federation, has been authorized in 2005. New “Classification” must take effect since January 1, 2009. Methodical recommendations on its application have been authorized in 2007.

The basis of this report is the experience of the overestimation of the undistributed fund fields reserves for the Western Arctic water areas - Barents, Pechora and Kara Seas - in accordance with the new “Classification”.

The first field in the Arctic shelf (Murmansk gas field) was opened in the Barents Sea in 1983. It appeared to be most complex by it’s structure - 23 productive layers, united into 4 horizons. For five years 8 wells were drilled on the field, two of which were liquidated for the technical reasons. Then one more season the tests of wells proceeded.

North Kildinskoe gas field was opened in the Barents Sea in 1985. 3 wells were drilled. One well was liquidated for the technical reasons, one – appeared behind a contour of a field. Pomorskoe gas-condensate field was opened in the same year in the Pechora Sea by one well; and Gulyaevskoe oil-gas-condansate field - also by one well – was opened in 1986.

The largest sea field - Shtokmanovskoe - was opened in 1988. Five wells were required for it’s exploration; 2 additional wells were drilled later. The first petroleum field was opened in the Pechora Sea in 1989. It’s exploration also required 5 wells.

In the same year the first field – Rusanovskoe gas-condensate field - was opened in the Kara Sea by 2 wells, one of which appeared behind a contour of productivity. In 1990 Ludlovskoe gas field in the Barents Sea and Leningradskoe gas-condensate field in the Kara Sea were opened. In both cases, it was required to drill two wells. Two wells were drilled also on Ledovoe gas-condensate field, discovered in the Barents Sea in 1992. This field completed unprecedented number of the discoveries in the Soviet period of the Western Arctic offshore study.

10 fields were opened in 10 years, including 3 unique fields; the reserves of 3 additional fields exceed 100 billion m3. These discoveries on the totality were noted by State Prize in 1994. In their presentation to the high award it was noted: “The discovery the majority of fields is produced by the first prospecting well. Exploration and calculation of reserves were conducted with a minimum quantity of wells. This predetermined the extremely high economic effect of entire geological survey process, which is composed of the savings of inputs for drilling of several exploration wells and profit for the realization of the additional production, obtained due to shortening of the period of exploration and accelerated by several years of introduction into the development of fields”.

Further fate of these fields has been formed differently. Only two fields: Shtokmanovskoe – biggest on the reserves - and Prilazlomnoe - only petroleum field - appeared in the distributed fund with their subsequent additional exploration for the preparation for the development. The most complex on the structure Murmansk field was preserved. The remaining fields, explored by 1- 2 wells, until now, count as exploring ones and are in the undistributed resource fund. The summary reserves of gas of 8 fields of the undistributed fund of Western Arctic shelf are evaluated in 2.7 trln. m³, including 565 bill. m³ or 20.9% reserves on the category C1.

Five largest of these fields - Leningradskoe, Rusanovskoe, Ledovoe, Ludlovskoe, and Murmanskoe are related to the objects of federal value by the order of government RF dated November 28, 2007. They have strategic value for providing of an energy national safety, and they are taken into account in the plans of joint stock company “Gazprom” on increase in the reserves of gas for the period until 2020. The official registration of licenses to exploration and development of the reserves of Ledovoe (in 2009) and Ludlovskoe (in 2010) fields is assumed.

In connection with these circumstances there are two questions : 1- to what extent reliable and proved the initial estimation of the reserves of these fields; 2 - how will the structure of the initially estimated reserves change with their overestimation in accordance with the categories of new “Classification”.

Substantiation of reserves by drilling. 22 wells by summary volume 64.1 thous.m were drilled on 8 fields, including: 17- prospecting and 5 - exploration wells. From them 3 wells were liquidated for the technical reasons, without having carried out geological tasks; 4 wells appeared behind a contour of productivity. Tests were carried out on 13 wells, in such cases: on Murmanskoe field 5 wells have been tested, on the Ludlovskoe field 2 wells have been tested; on the remaining six fields - 1 well has been tested apiece; on the Leningradskoe and Ludlovskoe fields, one well apiece was acknowledged productive according to the GIS results.

Methods of the separation of the reserves on the category C1. During the estimation of the reserves of the fields of Western Arctic shelf in the different years the different methods of the sections isolation for the calculation of the reserves of the category C1 were used all around wells drilled and yielded positive results with the tests.

1983. On Murmanskoe field the reserves of the category C1 were calculated in the limits of the gas-water contacts, not covered by any well. Reserves were evaluated entirely on the category C1 for 6 layers of 21, for 15 layers - on the categories C1 and C2. The portion of the reserves of the category C1 on the field is as a whole 50.2%.

1985 – 1986. On Severo-Kildinskoe (1 layer), Pomorskoe (1 layer) and Severo-Gulyaevskoe (2 layers) fields the reserves of the category C1 were calculated within the framework of the circular contour with a radius of 2 km (for the gas) and 1 km (for the oil). The portions of the reserves of the category C1 in the summary extracted reserves of these fields composed, correspondingly, 32.7%, 27.4% and 17.7%.
1989. The circular contour with a radius of 4 km was used the only time for calculating the reserves of the category C1 on the Rusanovskoe field, which consists of 7 layers. The portion of the reserves of the category C1 is 30.9%.

1990- 1992. The rectangular contour by width of 4 km, with the length of 13.2 km, 12.0 km and 23.2 km, respectively, for calculating the reserves on the category C1 on Leningradskoe (5 layers), Ludlovskoe (1 layer) and Ledovoe (4 layers) fields was used. It connects two drilled wells. The portions of the reserves of the category C1 comprise 6.8%, 37.9% and 21.7%.
Not only fields, discovered into the different years, but also the separate layers in the limits of multi-stratified fields are characterized by the methods of the isolation of the sections of the category C1 reserves calculation – for example Leningradskoe and Ledovoe fields. It is obvious that estimation of the reserves of the category C1 of these fields, made with the use of different methodical means, are nonequivalent and, actually, they are not compared.

Overestimation of reserves in accordance with the new “Classification”. Two groups of the reserves are separated on the basis of the economic effectiveness of development: commercial and noncommercial ones (article 18 of methodical recommendations). A commercial reserves include the reserves, whose involvement in the development at the moment economically expedient and is technically and technologically possible (article 19). They are subdivided into the normally profitable and the conditionally profitable (article 20). The development of the latter at the moment of estimation does not ensure acceptable economic effectiveness, but their development can become economically possible under specific conditions, evaluated over the long term next 5 years from the time of estimation. The number of these conditions includes: a price change of oil and gas; the appearance of new markets for sale or technologies of development; the creation of new oil and gas infrastructure; the possibility of their development not autonomous, but joint with nearby objects (article 22 and 32).

The noncommercial reserves include the reserves of the fields, whose involvement in the development at the moment of estimation is economically inexpedient, or it is technically or technologically impossible. The preserved fields and the fields, considerably removed from the transport ways and infrastructures of oil and gas production, also enter into this group. Reserves are calculated and considered only in the geological form on the fields with the noncommercial reserves (article 23).

The fields of Arctic shelf are isolated separately as fields definitionally with noncommercial reserves at the moment of estimations (article 33):
“The isolation of the group of noncommercial reserves by reason of conditions of inaccessibility and absence of the real technologies of the development of fields (fields on Arctic shelf with the depths, inaccessible for the contemporary technological tools, under the conditions of continuous ice cover and drifting ices and others) is recommended to achieve on the basis of the qualitative characteristic of the impossibility of development without the quantitative assessment of economic criteria”.

Results of the estimation of the economic effectiveness of the development of the fields of the undistributed fund of Western Arctic shelf, executed in VNIGRI (All-Russia Petroleum Scientific Research Exploration Institute) by G.A. Grigoryev in 2008, in accordance with the Methodical recommendations, show the following: the reserves of these fields can’t be related to the group of normally profitable; the reserves of the Ledovoe and Ludlovskoe fields can be referred to the group of conditionally profitable ones with the condition of their development on the infrastructural base of the Shtokmanovskoe field; the reserves of the Leningradskoe, Rusanovskoe, Murmanskoe, Severo-Kildinskoe, Severo-Gulyaevskoe and Pomorskoe fields are related to the group of noncommercial.

In accordance with the new “Classification”, the isolation of the reserves of categories A, B and C1 is produced in the bounds of elementary sections - squares with the wells in the center and with sides, equal to the distance between wells of operational network, determined by analogy or by expert method (article 9).

The experience of the application of a new procedure to the fields of the undistributed fund of Arctic shelf shows (Novikov, Gazhula, 2008) that the areas of calculation of C1 category reserves much decrease in comparison with the initial estimation. Most significant (many times) this decrease is for the largest fields, discovered and evaluated in period 1989 - 1992 - Rusanovskoe, Leningradskoe, Ludlovskoe and Ledovoe; and also for the Murmanskoe field, the first opened.

Conclusions
• The experience of the use of Methodical recommendations regarding the application of a new “Classification” for the overestimation of the reserves of the fields of the undistributed fund on Arctic shelf reveals their ambiguity and discrepancy.
• The initial estimation of the reserves of these fields was executed on the basis of the extremely limited quantity of the wells and with the use of different methods of the isolation of the sections of the C1 category reserves calculation.
• The initial reserves of the category C1 of these fields will significantly decrease with the overestimation. The reserves of category B can be isolated only on two conditionally profitable fields: Ludlovskoe (2 wells) and Ledovoe (1 well).
References
Novikov Y.N., Gazhula S.V. Special features of the estimation of the hydrocarbon fields on the Arctic shelf of Russia and their overestimation in accordance with the new classification of reserves/ Nephtegazovaya geologia. Theory and the practice: Electr. Scientific. Jour. VNIGRI. 0420800064\0008. https://www.ngtp.ru/rub/6/13_2008.pdf - St. Petersburg: VNIGRI, 2008, 19 p.

Oil and gas of Arctic shelf 2008