Geology, geography and global energy

Scientific and Technical Journal

STRUCTURAL AND TEXTURAL AND GEOPHYSICAL PROPERTIES OF THE KUNGUR SALT-BEARING SECTION OF THE ASTRAKHAN ARCH

2020. №1, pp. 49-57

Ushivtseva Lyubov F. - Astrakhan State University, ushivceval@mail.ru

Knowledge on geological factors of the section of the wells to be drilled as well as forecast of potential drilling complications are always important in any oil and gas production region. This issue is particularly relevant during construction of wells in salt basins with occurrence of salt with various composition - halite, bischofite, carnallite. The heterogeneity of the salt - bearing section texture to - gether with rocks of different lithological and mineral composition, with various geological - geophysical and mechanical properties, formation and pore pressure gradients are responsible for various complications: rocks showings, plastic movement of salts and viscous plastic clays, which cause casing buckling; mud loss in intra - salt layers; natural brine shows; These types of complica - tions are registered during construction of wells in the Dnieper-Donetsk, East Kuban, Amudarya, and Caspian depressions, and most of them are associated with salts and inter - salt deposits. Complications elimination leads to wells costs and construction period increase, therefore, forecast on project wells geological factors are essential when drafting design documentation. This article reviews structural and textural features and geological and geophysical parameters of rocks in the salt section of the Astrakhan arch uplift, and it analyzes nature of complications triggering events. Originality. The con - nection between the following geological factors lithological composition, structural and textural features, geological and geophysical properties of intra - salt rocks and salts, and technological factors (increased or insufficient density of clay mud) with occurring complications. Summary . Knowledge on geological factors of the section of the project well at the pre - design stage, to be drilled at the pre - project stage, incompatibility of salt - bearing, suprasalt, mainly terrigenous, and subsalt carbonate section allow for the following: to choose the adequate well design, to pick mud clay individual pa - rameters for penetration of each section, to plan well intervention measures in the event of drilling complications, to reduce geological risks, and bring the well to the target depth.

Key words: солянокупольная тектоника, внутрисолевые пласты, рапопропроявления, аномальновысокие пластовые давления, поглощения, трещинная проницаемость, структурно - текстурные особенности, неоднородности, salt dome tectonics, intra-salt layers, natural brine show,

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