Solving the Inverse Problem of Geomechanical Monitoring to Improve the Efficiency of Field Development

The purpose of geomechanical monitoring at mineral deposits, including oil and gas, is to control the state of the rock mass, forecast possible risks and complications at all stages of the field's life: reservoir and caprock integrity failure, violation of the integrity of drilling and system of well completion, infrastructure facilities. The paper suggests approaches to the organization of a geomechanical monitoring system based on observations of displacements and deformations of the ground surface (or seafloor) during the development of reservoir and target interval. There are analytical and numerical approaches have been tested on simple models with pore pressure changes, considering the heterogeneity of elastic-strength properties.

Distributed Fiber Optic Strain Sensing for Geomechanical Monitoring: Insights from Field Measurements of Ground Surface Deformation

In recent years, distributed fiber optic strain sensing (DFOSS) technology has demonstrated a solution for continuous deformation monitoring from subsurface to surface along the wellbore. In this study, we installed a single-mode optical fiber cable in a shallow trench to establish an effective technique for ground surface deformation mapping. We conducted three experimental field tests (iron plate load, water tank filling up load, and airbag inflation) in order to confirm the strain sensitivity of DFOSS for static loads, dynamic overload, excavation, subsidence, and uplift. This paper also presents two installation methods to couple the fiber cable with the ground under various environmental conditions; here, the fiber cable was installed in a shallow trench with one part buried in the soil and another part covered with cement. Our results suggest that covering the cable with cement is a practical approach for installing a fiber cable for ground surface deformation monitoring. By combining this approach with wellbore DFOSS, accurate surface–subsurface deformation measurements can be obtained for three-dimensional geomechanical monitoring of CO2 storage and oil and gas fields in the future.

Overcoming Hole Instability in Highly Deviated Wells in the Kafr El Sheikh Shale, Offshore Mediterranean, Egypt

Drilling challenges in offshore Nile Delta have been largely documented in the literature. Operators are often confronted with drilling problems related to shale swelling, cavings, tight holes in combination with increased risks of lost circulation in some of the highly depleted formations. The Kafr El Sheikh shale in particular, has been linked to many instances of wellbore instability, due to its mineralogical composition (estimated to be mostly smectite, >70%). From offset well drilling experience, it could also be noticed that insufficient mud weight was often used to drill through the Kafr El Sheikh Shale, causing wellbore failure in shear due to lack of support of the wellbore wall. In the past, multiple mud weight designs have been implemented relying solely on pore pressure as lower bound of the mud window. With the increased use of geomechanics, it has been demonstrated that the lower bound should be taken as the maximum of the pore pressure and borehole collapse pressure, thus accounting for the effects of formation pressure, horizontal and vertical stresses, rock properties as well as wellbore trajectory. It has been proven that slight overpressure is often encountered halfway through the Kafr El Sheikh formation, which would typically result in slightly higher borehole collapse pressures. In the study fields, the operator expressed interest in drilling highly deviated wells (> 60-70 degrees). This raised concerns for increased drilling challenges, especially in the Kafr El Sheikh. A comprehensive and systematic risk assessment, design of a fit-for-purpose solution and its implementation during drilling took place in the fields of interest. Offset well data analytics from the subject fields supported a holistic evaluation of drilling risks associated with the Kafr El Sheikh, providing good understanding of stress sensitivity on deviation, azimuth and lithology. Upon building a robust geomechanical model, calibrated against offset well drilling experience, pre-drill mud weight and drilling practices recommendations were provided to optimize the drilling program. Near real-time geomechanical monitoring was implemented which helped to manage the model uncertainties. The implementation of a holistic risk assessment, including geomechanical recommendations and near real-time geomechanical monitoring, was effective to lead the drilling campaign successfully. As a result, three high angle wells (> 60-70 degrees) were drilled through the challenging Kafr El Sheikh formation without any hole instability. An integrated risk assessment of hole instability, managed in stages (pre-drill and during drilling), has helped to understand and simulate the behaviors of the formation. Proactive decisions have established a controlled drilling environment for successful operations.

Mathematical tools and software for the distributed geophone network of Prognoz-ADS geomechanical monitoring system

Introduction. The article considers the problems of the present-day algorithm of acoustic emission events location in Prognoz-ADS geomechanical monitoring system. The ways of solving the flaws in the applied algorithm have been proposed with the account of the specified requirements. Research aim is to propose certain solutions aimed at achieving higher accuracy of seismoacoustic events coordinates calculation; to solve the flat antenna problem and get the opportunity of assessing the efficiency of separate observing network elements; develop the structure of a new location algorithm and calculate its preliminary complexity. Methodology. It is proposed to correct the problems of the existing algorithm by constructing the velocity map of the controlled object and assessing the efficiency of seismoacoustic receivers and data on the observing network sensitivity in various sections of the rock mass. Results. The article provides logical structure of the developed algorithm with complexity O(n). It is proposed to solve the flat antenna problem by using data on seismic receivers complex sensitivity. Certain media of collecting information on the observing network state and signal propagation velocities at the controlled object have been introduced. Summary. The designed algorithm provides for multiple parameters variation, many of them are not taken into account in the existing location method of Prognoz-ADS system. The indicated characteristics selection and the efficient use of the calculating tool’s hardware resources will make it possible to obtain a more accurate and universal location algorithm.

MONITORING OF DISPLACEMENTS OF OBJECTS OF TERRESTRIAL SURFACES BY INTERFEROMETRY METHOD

Geomechanical monitoring is a system of observations of the state of the geological environment, the processes of displacement of rocks and the earth's surface, geomechanical and hydrodynamic processes in a rock mass, interpretation of the results of observations, the formation of judgments about the state of the rock mass as a whole and the forecast of parameters of stable slopes. To determine the displacement of the earth's crust of the Akbakay field, the technology of terrestrial radar interferometry was used. Which is used by only a few research institutes and organizations in the world. In satellite radar interferometry, the promptness to obtain an actual spatial information about the Earth's surface is an important requirement for modern Earth remote sensing data, along with high spatial resolution, as well as geometric accuracy. The operational efficiency is one of the main advantages of radar systems for remote sensing of the Earth or a system of instruments synthesized by radar. Geomechanical monitoring and research on geodynamic polygons reveal wide opportunities for studying vertical movements of the earth's crust. In this work, the most important point is the scanning of the terrain and objects around the scanner standing point, i.e. Scanning special marks with the maximum resolution, which allows you to get a cloud of points.

GEOMONITORING OF STABILITY STATE OF CAREER SLOPES

The development of geomechanical monitoring of the state of near-surface arrays of quarries is an urgent task for predicting and ensuring the stability of quarry slopes. This is preceded by a detailed study of the geological and geological situation of instrument massifs, the laying of reference and working benchmarks, the methodology for measuring and analyzing the obtained displacements of instrument massifs. Particular attention is paid to the analysis of the accuracy of instrumental observations with the help of an electronic total station and an optical reflector, as well as to the identification of optimal observation schemes at the quarry, which make it possible to establish rational parameters for making measurements. The distance between the reflector and the total station is set to 500m, which allows measurements to be made within ± 3 mm. The proposed measurement technique was tested in the quarries of Kazakhstan.