NEW DATA OF A COMPREHENSIVE GEOMECHANICAL AND PETROPHYSICAL STUDY OF THE DOLGINSKOE FIELD RESERVOIR PROPERTIES

Abstract

The relevance of the research is caused by the need to reduce well drilling time on the Arctic shelf due to the limited navigation season and increased accuracy in assessing reserves obtained from the results of testing exploratory wells at the Dolginskoe field. The research results make it possible to select the optimal technology for drilling carbonate reservoirs of the Dolginskoe field, as well as to ensure the stability of the wellbore and preserve reservoir properties, establish the relationship between reservoir properties of rocks and stresses in productive formations, and justify the technological parameters of field development. The purpose of the research is to assess the influence of the composition, structure, filtration-capacitive properties of reservoir rocks and acting stresses on their permeability. Objects. Carbonate reservoir rocks of the Lower Permian and Carboniferous age were drilled in a well from a depth of 2982 m to a bottomhole of 3175 m and are characterized by pelitomorphic limestones, organogenic-detrital and cryptocrystalline varieties. Methods. The research was carried out by modern laboratory methods, including mercury porosimetry, the method of nuclear magnetic resonance, as well as a unique test bench of the Institute for Problems in Mechanics of the Russian Academy of Sciences. Results. On the basis of quantitative data of lithological and petrophysical properties, the authors have studied the deformation and strength characteristics of rocks from the probably productive part of the section of the Severo-Dolginskaya no. 1 well, which was not tested due to the short season of offshore operations. The data were obtained on the structure of the pore space, acoustic properties, density, porosity and permeability (including in reservoir conditions), residual water saturation, etc. The deformations of samples of rocks of a carbonate deposit in three directions and their relationship with permeability under stress conditions were studied. The new information obtained as a result of the work makes it possible to more accurately select the properties and component composition of the drilling fluid in order to control the repression, the formation of a thin impermeable filter cake, and to minimize the physicochemical interactions between the mud filtrate and formation fluids.

Keywords

• dolginskoe field
• carbonate reservoirs
• geomechanics
• petrophysics
• nuclear magnetic resonance
• triaxial loading
• permeability
• porosimetry