НЕФТЯНАЯ ПРОВИНЦИЯ

Abstract

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The process of drilling and fastening wells is very complex in engineering terms, as it is accompanied by the destruction of rocks of different properties. The stability of rocks is sharply reduced in the presence of different types of water. In clay rocks and salts, the processes of moistening, swelling and dispersion play a significant role, causing a weakening of the structural bonds between the rock particles. In order to prevent complications during the well wiring, it is necessary to study the causes of changes in the properties of rocks in various geological conditions, as well as to determine the nature of the violation of the stability of the wellbore drilled in terrigenous rocks containing clay inclusions, as well as in salt and inter-salt deposits. The results of studies of changes in the properties of clay rocks in the formation of the wellbore during drilling. Experimental data on the determination of mechanical properties of different lithotypes of terrigenous clay rocks at different depths are systematized. An important conclusion that follows from the constructed dependences: with a depth of more than 1500 m, the compressive strength of clay rocks (σsj) becomes less than the skeletal stresses in the range of anomalous reservoir pressure (abnormally low – ALRP and abnormally high – AHRP) from 0.25≤Ka<1.0 (ALRP), and from depths of 3000 m and more – in the range of 1.0<Ka≤1.5 (AHRP). The areas of changes in the stress state of the bottomhole formation zone (BFZ), where there is a violation of the stability of the wellbore (scree, landslides, cavern formation, narrowing of the trunk) On the basis of the calculations, and builds established that the abnormal ratio of the anomalous Ka≥2,0 with depths greater than 3000 m. Most of the obtained data concentrated in the range of skeletal stresses in the PZP when 1,22≤Ka≤2,0. For five wells in which there was a violation of the trunk, skeletal stresses are in the Ka>2.0. On the basis of statistical data of change of properties of clay mountain with depth the technique of the prevention of complications at conducting of wells in difficult mountaingeological conditions is developed.

Key words:

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Bottomhole formation zone, drilling, workover, complications when posting wells, the stability of the borehole walls and clay rocks, strength rocks, skeletal stresses, rock pressure, formation pressure, pore pressure, downhole pressure, density of rocks, density of drilling mud.

References

 

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Authors

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Nifantov V.I., Chief researcher of the underground gas storage Center, doctor of technical Sciences, Academician of the Russian Academy of natural Sciences in the section of oil and gas, Limited Liability Company «Research Institute of Natural Gas and Gas Technologies - Gazprom VNIIGAZ» (LLC «Gazprom VNIIGAZ»), Moscow, Russian Federation E-mail: v_pischukhin@vniigaz.gazprom.ru

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Melnikova E.V., researcher at the laboratory of design and analysis of gas condensate and oil and gas fields development at the field development Center, Limited Liability Company «Research Institute of Natural Gas and Gas Technologies -Gazprom VNIIGAZ» (LLC «Gazprom VNIIGAZ»), Moscow, Russian Federation E-mail: v_pischukhin@vniigaz.gazprom.ru

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Pischukhin V.M., a leading researcher at the Department of experimental research experimental center, candidate of technical Sciences, academician of the international Academy of Sciences of applied radioelecronics, corresponding Member of the Academy of natural Sciences in the section of oil and gas, Limited Liability Company «Research Institute of Natural Gas and Gas Technologies -Gazprom VNIIGAZ» (LLC «Gazprom VNIIGAZ»), Moscow, Russian Federation E-mail: v_pischukhin@vniigaz.gazprom.ru

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Kuznetsov S.A., Deputy head of the laboratory of technological design of underground gas storage center UGS, Limited Liability Company «Research Institute of Natural Gas and Gas Technologies -Gazprom VNIIGAZ» (LLC «Gazprom VNIIGAZ»), Moscow, Russian Federation E-mail: v_pischukhin@vniigaz.gazprom.ru

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Makarev O.V., Deputy head of Directorate, Public joint-stock company «Gazprom» (PJSC «Gazprom»), Moscow, Russian Federation E-mail: O.Makarev@adm.gazprom.ru

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For citation:

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V.I. Nifantov, E.V. Melnikova, V.M. Pischukhin, S.A. Kuznetsov, O.V. Makarev Prognoz izmenenija prochnosti gornyh porod ot glubiny [Forecast of changes of rock strength with depth]. Neftyanaya Provintsiya, No. 1(17), 2019. pp. 141-155. DOI https://doi.org/10.25689/NP.2019.1.141-155 (in Russian)