Geological model and optimal well placement substantiation at the western part Tyumen suite layers of Khanty-Mansiysk Autonomous Okrug — Ugra

The middle Jurassic Tyumen sediments have been involved in the development of oil facilities in the territory of the Khanty-Mansiysk Autonomous Okrug — Ugra for the last decade. The Jk2-5 formation is represented by complex interlayering of poorly permeable sandy-aleurite lenses and clay barriers with low reservoir properties. Recoverable oil reserves of the Jk2-5 formation on the Krasnoleninsky arch amounts to several hundred million tons. According to the collector permeability, the reserves of the object are classified as hard-to-recover. There are no effective technologies to involve such reserves in the development now. Standard methods of drilling and operation of inclined wells doesn't allow achieving acceptable oil production rates under these reservoir conditions. Based on the analysis of seismic survey data, correlation of well sections, field information, a geological model of a productive reservoir on the Krasnoleninsky arch was created. The multi-step hydrodynamic calculations made it possible to clarify the parameters of the profile of horizontal wells, the number and configuration of operations for multi-stage hydraulic fracturing. Based on the results of the research, recommendations were developed to well placement, drilling and well operation for specific field areas in order to increase the oil resource development efficiency.

Numerical Modelling of Clay Seal Maturation in Deep Boreholes with Nuclear Waste

One of the major challenges of high-level nuclear waste (HLW) isolation in deep boreholes is to anticipate the maturation behaviour of swelling clay when the waste, surrounded by dense clay encased in perforated tubes, is submerged into the borehole mud. The ultimate homogeneity of this clay seal acting as a barrier is expected to stabilize the borehole and to prevent possible leakage of radioactivity. In this study, a numerical model for predicting the maturation of the clay barrier has been developed. In the model, the water transport is controlled by the differences in the suction potential and the permeability. The model is able to simulate the maturation process, both the expeditious water transport and the clay migration into the surrounding mud, from beginning to end. Results from laboratory tests of the clay maturation were compared with the predictions made by the model. They are in good agreement, but refinement is proposed by taking the impact of the tube perforation on the maturation rate into more consideration. The proposed numerical model will also be useful in selecting a suitable design for clay barriers in HLW boreholes. Different combinations of clay dimensions and initial densities of mud and dense clay can thus be studied to determine the final homogenization and the end densities.