An Advanced Ultra-Deep Resistivity Mapping Sensor Reduced Reservoir Uncertainty and Eliminated the Need for a Pilot Hole for the First Time; A Case Study from Offshore Abu Dhabi

The high reservoir uncertainty, due to the lateral distribution of fluids, results in variable water saturation, which is very challenging in drilling horizontal wells. In order to reduce uncertainty, the plan was to drill a pilot hole to evaluate the target zones and plan horizontal sections based on the information gained. To investigate the possibility of avoiding pilot holes in the future, an advanced ultra-deep resistivity mapping sensor was deployed to map the mature reservoirs, to identify formation and fluid boundaries early before penetrating them, avoiding the need for pilot holes. Prewell inversion modeling was conducted to optimize the spacing and firing frequency selection and to facilitate an early real-time geostopping decision. The plan was to run the ultra-deep resistivity mapping sensor in conjunction with shallow propagation resistivity, density, and neutron porosity tools while drilling the 8 ½-in. landing section. The real-time ultra-deep resistivity mapping inversion was run using a depth of inversion up to 120 ft., to be able to detect the reservoir early and evaluate the predicted reservoir resistivity. This would allow optimization of any geostopping decision. The ultra-deep resistivity mapping sensor delivered accurate mapping of low resistivity zones up to 85 ft. TVD away from the wellbore in a challenging low resistivity environment. The real-time ultra-deep resistivity mapping inversion enabled the prediction of resistivity values in target zones prior to entering the reservoir; values which were later crosschecked against open-hole logs for validation. The results enabled identification of the optimal geostopping point in the 8 ½-in. section, enabling up to seven rig days to be saved in the future by eliminating a pilot hole. In addition this would eliminate the risk of setting a whipstock at high inclination with the subsequent impact on milling operations. In specific cases, this minimizes drilling risks in unknown/high reservoir pressure zones by improving early detection of formation tops. Plans were modified for a nearby future well and the pilot-hole phase was eliminated because of the confidence provided by these results. Deployment of the ultra-deep resistivity mapping sensor in these mature carbonate reservoirs may reduce the uncertainty associated with fluid migration. In addition, use of the tool can facilitate precise geosteering to maintain distance from fluid boundaries in thick reservoirs. Furthermore, due to the depths of investigation possible with these tools, it will help enable the mapping of nearby reservoirs for future development. Further multi-disciplinary studies remain desirable using existing standard log data to validate the effectiveness of this concept for different fields and reservoirs.

Capturing Fault Effects in Thin Reservoirs for Geosteering Improvements in Developing Offshore Carbonate Fields

Analogue outcrops can be used to prepare geoscientists with realistic expectations and responses for Geosteering ultra-long horizontal wells (ERD) in thin reservoirs with different scales of faults, and uncertainty in fault zone parameters and characteristics. Geosteering ultra-long horizontal wells in specific, thin, meter-thick target zones within reservoirs is challenged when sub-seismic faults are present or where seismic scale fault throw and fault location is ill-defined or imprecisely known. This paper defines the challenge of how analogue outcrops can be used to prepare geoscientists with realistic expectations and responses to such operational difficulties in faulted carbonates, irrespective of the tools employed to characterize encountered faults. Geosteering wells in reservoirs with different scales of faults and uncertainty in fault zone character and detection limits can lead to: (i) extensive ‘out of zone’ intervals and (ii) undulating wellbores (when attempting to retrieve target layer positioning), whereby well productivity and accessibility are compromised. Using faulted carbonate field analogues can direct the operation geologist's geosteering response to such faulted scenarios. Descriptions from outcrops are used to address subsurface scenarios of marker horizon(s) and their lateral/spatial variability; diagenesis related to faults at outcrop and expected variations along wellbore laterals in the oilfield. Additionally, offsets/throws, damage zone geometries for thin-bed reservoir understanding of fault zone effects in low-offset structures. Appreciation of faults in outcrops allows an understanding of expectations whilst drilling according to the following: (1) Scales of features from seismic to sub-seismic damage zones: what to expect when geosteering within / out of zone, across faults with indeterminate throws. (2) Understandings from 3D analogues/geometries applied predictively to field development, targeting specific thin reservoir zones / key marker beds. Several oil- well case-examples highlight the response in steering wellbores located within specific thin target zones whereby faults were expected, but where fault throw differed significantly to what was anticipated from initial seismic interpretation. Examples elucidating the application include a meter-thick dolomite zone within a very thick limestone reservoir where injector and producer wells are completed, where the wellbore remains within reservoir but out of specific target zone (how to marry smooth wellbore with layer conformance). Furthermore, for very thin reservoirs primarily located within non-reservoir carbonates, minor faults would misdirect wellbore into argillaceous limestone above or below the reservoirs. Faulted zones with water influx mapped from LWD where modelled property responses can be better characterized by low-offset faults with compartmentalizing effects for completion strategies. Even with an extensive suite of logs to characterize fault zones, the objective of Geosteering a well continuously within zone becomes difficult. Selected key tools are required for success. Directly using Early Cretaceous reservoir analogues, with specific fault types and displacements, critically aid geosteering practices for QA, prediction and learnings.

Experimental use of stereotactic radiosurgery for non-invasive interventions in arrhythmology

Purpose. The experimental study aimed to study the effects of stereotaxic radioablation of various doses on the myocardium of the atria, ventricles and atrioventricular (AV) node in the long term (up to 6 months); as well as assessment of collateral damage during radioablation.Methods. The study comprised 4 domestic pigs. The animals were 10-12 weeks old, the average weight was 30±2.7 kg. A linear accelerator was used for the experiment. Each animal underwent radiation exposure in different areas: 1st animal - AV node (dose 35 Gy), 2nd animal - AV node and the apex of the left ventricle (LV) (dose 40/35 Gy, respectively), 3rd animal - pulmonary veins (PV) and left atrium (dose 30 Gy), 4th - AV node and LV free wall (dose 45/40 Gy). Under intravenous sedation with hemodynamic monitoring, contrast-based CT of the heart was performed to assess the degree of displacement of the heart chambers in one respiratory and cardiac cycle and to assess the anatomy of the chambers of the heart and adjacent organs. The allocation and the contouring of the target zones were carried out in three projections: axial, frontal and sagittal. For electrocardiographic control, a loop recorder was implanted in each animal. The average exposure time was 11±7 minutes. After a follow-up period, morphological examination of the autopsy material was performed.Results. The average follow-up period after ablation was 134.75±77.34 days. The electrophysiological effect of the ablation was achieved in cases of complete AV-block development. This effect was developed in 2 out of 3 animals, where AV-node was exposed: 2nd animal - 40 Gy on 108th day of observation and 4th animal - 45 Gy on 21st day of observation. No cardiac tachyarrhythmia was recorded in the animals. The results of myocardium macro- and microscopic examination showed significant changes in the target zones. These areas had precise but uneven damage boundaries, which were within the planned ones (conformal exposure with a high degree of precision). The transmural nature of the changes was noted as well. Massive fields of fibrous tissue of various degrees of maturity (with a predominance of subepicardial localization) with focal hemorrhages of various ages and granulations were detected, which were surrounded by cardiomyocytes with coagulated and vacuolated cytoplasm.Conclusion. The use of non-invasive stereotactic treatment of tachyarrhythmias has high prospects in modern electrophysiology as an alternative ablation method.

Fracturing Experience of Tyumenskaya and Vikulovskaya Formations: Application of Novel Low-Viscosity Fracturing Fluids as an Alternative to Guar-Based Fluids

Tyumenskaya and Vikulovskya stratas are the major development objects for Rosneft subsidiary – RN- Nyaganneftegaz, characterized by close location of target zones to other layers, breakthrough in which is not desirable. Thus, target zones of Tyumenskaya group of formations are located close to Abalakskaya strata, and Vikulovskaya group of formations is described by close location of the target hydraulic fracturing intervals to the water-saturated layers. Risks of multi-stage hydraulic fracturing are high due to the use of synthetic geological and geomechanical models and synthetic logging associated with different sections of horizontal wells. The article presents the implementation experience of specifically developed technological solution in order to increase profitability of development and production of hydrocarbons and decrease the risks of ineffective stimulation: use of low-viscosity viscoelastic hydraulic fracturing fluids based on synthetic polymer- polyacrylamide with inherited ability to control fracture height growth without a need in significant reduction of proppant volume. The work performed on development and introduction of novel low-viscosity fluids based on polyacrylamide on Vikulovskaya and Tyumenskaya formations - RN-Nyaganneftegaz development objects has become a new stage in the history of hydraulic fracturing of these formations, and as well as for other oilfields with similar geological structure and field development conditions. The gained experience formed a basis for the effective implementation of similar hydraulic fracturing fluid systems and increasing of well productivity following in the result of well stimulation.

Combined Usage of Different Geosteering Methods and Vendor Independent Bed Boundary Mapping in Complex Geological Environment on a Real-Life Example from West Kazakhstan

Summary Drilling lateral wells nowadays is considered to be the most widely used method for producing hard-to-recover hydrocarbon reserves. Technologies used while geosteering the well are developing rapidly making high-level geosteering the key for cutting costs on drilling and enhancing well production. Due to low prices for hydrocarbons, oil companies are trying to find new, up-to-date approaches that will allow them to reduce capital and operating expenses while still enhancing the efficiency of drilling wells in target zones. One of such technology will be shown in this abstract through the example of a successfully drilled well in Akingen oilfield, Republic of Kazakhstan.

The Patient-Specific Combined Target Zone for Morpho-Functional Planning of Total Hip Arthroplasty

Background Relevant criteria for total hip arthroplasty (THA) planning have been introduced in the literature which include the hip range of motion, bony coverage, anterior cup overhang, leg length discrepancy, edge loading risk, and wear. The optimal implant design and alignment depends on the patient’s anatomy and patient-specific functional parameters such as the pelvic tilt. The approaches proposed in literature often consider one or more criteria for THA planning. but to the best of our knowledge none of them follow an integrated approach including all criteria for the definition of a patient-specific combined target zone (PSCTZ). Questions/purposes (1) How can we calculate suitable THA implant and implantation parameters for a specific patient considering all relevant criteria? (2) Are the resulting target zones in the range of conventional safe zones? (3) Do patients who fulfil these combined criteria have a better outcome score? Methods A method is presented that calculates individual target zones based on the morphology, range of motion and load acting on the hip joint and merges them into the PSCTZ. In a retrospective analysis of 198 THA patients, it was calculated whether the patients were inside or outside the Lewinnek safe zone, Dorr combined anteversion range and PSCTZ. The postoperative Harris Hip Scores (HHS) between insiders and outsiders were compared. Results 11 patients were inside the PSCTZ. Patients inside and outside the PSCTZ showed no significant difference in the HHS. However, a significant higher HHS was observed for the insiders of two of the three sub-target zones incorporated in the PSCTZ. By combining the sub-target zones in the PSCTZ, all PSCTZ insiders except one had an HHS higher than 90. Conclusions The results might suggest that, for a prosthesis implanted in the PSCTZ a low outcome score of the patient is less likely than using the conventional safe zones by Lewinnek and Dorr. For future studies, a larger cohort of patients inside the PSCTZ is needed which can only be achieved if the cases are planned prospectively with the method introduced in this paper. Clinical Relevance The method presented in this paper could help the surgeon combining multiple different criteria during THA planning and find the suitable implant design and alignment for a specific patient.

Ultra-Deep Resistivity Mapping Tool Provided Geostopping Solution to Reduce Uncertainty and Eliminated the Need for Pilot Holes for the First Time Offshore Abu Dhabi

Drilling horizontal wells in the mature giant carbonate fields offshore Abu Dhabi, where high uncertainty regarding the lateral distribution of fluids results in variable water saturation, is very challenging. In order to meet the challenges and reduce uncertainty, the plan was to drill pilot holes to evaluate the resistivity of the target zones and plan horizontal sections based on the information gained. To investigate the possibility of avoiding pilot holes in the future, an ultra-deep electromagnetic (EM) tool was deployed to map the mature reservoirs, identifying formation and fluid boundaries before penetrating them, avoiding the need for pilot holes. Prewell inversion modeling was conducted to optimize the spacing and firing frequency selection and to facilitate early real-time geosteering and geostopping decisions. The plan was to run the ultra-deep resistivity mapping tool in conjunction with shallow propagation resistivity, density, and neutron porosity while drilling the 8 ½-in. landing section. The real-time ultra-deep EM inversion was run using depth of inversions up to 120 ft., to be able to detect the reservoir early and evaluate the predicted reservoir resistivity. This would allow optimization of any geostopping decision. The ultra-deep EM tool delivered accurate mapping of thin reservoir layers while drilling the 8 ½ inch section, as well as enhanced mapping of low resistivity zones up to 85 ft. True Vertical Thickness (TVT) in a challenging low resistivity environment. The real-time EM inversion enabled the prediction of resistivity values in target zones prior to entering the reservoir; values were later crosschecked against open-hole logs for validation. The results enabled identification of the optimal geostopping point in the 8 ½-in. section, enabling up to seven rig days to be saved in the future by eliminating pilot holes, in addition to eliminating the risk of setting a whipstock at high inclination with subsequent milling operations. In specific cases, this minimizes drilling risks in unknown/high reservoir pressure zones by improving early detection of a formation tops, thus improving geostopping decisions. Plans were modified for a nearby future well and the pilot-hole phase was eliminated because of the confidence provided by these results. Deployment of the ultra-deep EM tool in these mature carbonate reservoirs may reduce the uncertainty associated with fluid migration. In addition, use of the tool can facilitate precise geosteering to maintain distance from fluid boundaries in thick reservoirs. Furthermore, due to the depths of investigation possible with these tools, it will help enable the mapping of nearby reservoirs for future development. Further multi-disciplinary studies remain desirable using existing standard log data to validate the effectiveness of this concept for different fields and reservoirs.

Hydrocarbon Mapping on Reservoir Carbonate Using AVO Inversion Method

Amplitude Versus Offset (AVO) inversion has been applied for reservoir analysis focused on the horizon carbonate Peutu and Belumai. Simultaneous inversion analysis is used to determine gas anomaly inside carbonate-rocks and it’s spread laterally around target zones. It is based on the fact that small Vpand Vs value changes are going to show the better anomaly to identify reservoir fluid content. The AVO inversion method applies angle gather data as the input and then it is inverted to produce P impedance (Zp) and S impedance (Zs). Zp and Zs are derived to produce Lambda-Rho and Mu-Rho that are sensitive to fluid and lithology. Value of Mu-Rho between 44–65 Gpa gr/cc while value of Lambda-Rho smaller than 10 Gpa gr/cc (for carbonate-rock filled by fluid). This research found that Lambda-Rho is the best parameter to show the existence of hydrocarbon in the case of gas. While Mu-Rho is the best parameter to show the differences in lithology.

Experimental use of stereotactic radiosurgery for non-invasive interventions in arrhythmology

Purpose. The aim of the experimental study was to study the effects of stereotaxic radioablation of various doses on the myocardium of the atria, ventricles and atrioventricular (AV) node in the long term (up to 6 months); as well as assessment of collateral damage during radioablation.Material and methods. The research was carried out on 4 domestic pigs. The animals were 10-12 weeks old, the average weight was 30±2.7 kg. Linear accelerator «TrueBeam», Varian was used for the experiment. Animals were divided into groups according to the zones of planned radiation exposure: 1st animal AV node (dose 35 Gy), 2nd animal AV node and the apex of the left ventricle (LV) (dose 40/35 Gy, respectively), 3rd animal pulmonary veins (PV) and left atrium (dose 30 Gy), 4th AV node and free wall of the LV (dose 45/40 Gy). Under intravenous sedation with hemodynamic monitoring, contrast-based CT of the heart was performed to assess the degree of displacement of the heart chambers in one respiratory and cardiac cycle and to assess the anatomy of the chambers of the heart and adjacent organs. The allocation and the contouring of the target zones were carried out in 3 projections: axial, frontal and sagittal. For electrophysiological control, loop recorders were implanted in each animal. The average exposure time was 11±7 minutes. The long-term follow-up period was 6 months, followed by morphological examination of autopsy material.Results. The average follow-up period after the experiment was 134.75±77.34 days. The electrophysiological effect of the ablation was achieved in cases of complete AV-block development. This effect was developed in 2 out of 3 animals, whose AV-node was exposed: 2nd animal 40 Gy on 108th day of observation and 4th animal 45 Gy on 21st day of observation. No cardiac arrhythmias were recorded in all cases. The results of macroand microscopic examination showed significant changes in the target zones. These areas had precise but uneven damage boundaries, which were within the planned ones (conformal exposure with a high degree of precision). The transmural nature of the changes was noted as well. Massive fields of fibrous tissue of various degrees of maturity (with a predominance of subepicardial localization) with focal hemorrhages of various ages and granulations were detected, which were surrounded by cardiomyocytes with coagulated and vacuolated cytoplasm.Conclusion. The use of non-invasive stereotactic treatment of tachyarrhythmias has high prospects in modern arrhythmology as an alternative ablation method.

Experimental use of stereotactic radiosurgery in non-invasive interventions in arrhythmology

Funding Acknowledgements Type of funding sources: None. Background Non-invasive stereotactic treatment with particle beam may be considered as a promising alternative to catheter ablation in patients with different types of tachyarrhythmias. Purpose the purpose of the experimental study was to develop a technique for stereotactic radioablation in order to create a stable functional and morphological damage in heart tissue with subsequent analysis of precision, efficiency and safety of the exposure in the long-term observation period. Materials and methods The research was carried out on four domestic pigs. The animals were 10-12 weeks old, the average weight was 30 ± 2.7 kg. Beam delivering linear accelerator was used during the experiment. Animals were divided into groups according to the zones of planned radiation exposure: 1st animal – atrioventricular (AV) node (dose 35 Gy), 2nd animal - AV node and the apex of the left ventricle (LV) (dose 40/35 Gy, respectively), 3rd animal - pulmonary veins muscle sleeves and left atrium (dose 30 Gy), 4th - AV node and free wall of the LV (dose 45/40 Gy, respectively). Under intravenous sedation with hemodynamic monitoring, contrast-based CT scan of the heart was performed to assess the degree of displacement of the heart chambers in one respiratory and cardiac cycle- and to assess the anatomy of the chambers of the heart and adjacent organs. The allocation and the contouring of the target zones were carried out in three projections: axial, frontal and sagittal. For electrophysiological control, loop recorders were implanted in each animal. The average exposure time was 11 ± 7 minutes. The long-term follow-up period was six months, followed by morphological examination of autopsy material. The study followed the "Principles of laboratory animal care". Results The average follow-up period after the experiment was 134.75 ± 77.34 days. The electrophysiological effect of the ablation was considered to be achieved in cases of complete AV-block development. This effect was developed in two out of three animals, whose AV-node was exposed: 2nd animal - 40 Gy on 108th day of observation and 4th animal - 45 Gy on 21st day of observation. No cardiac arrhythmias were recorded in all cases. The results of macro- and microscopic examination showed significant changes in the target zones. These areas had precise but uneven damage boundaries, which were within the planned ones (conformal exposure with a high degree of precision). The transmural nature of the changes was noted as well (pic. 1 A, B, C). Massive fields of fibrous tissue of various degrees of maturity (with a predominance of subepicardial localization) with focal hemorrhages of various ages and granulations were detected, which were surrounded by cardiomyocytes with coagulated and vacuolated cytoplasm (pic. 1 D, E, F). Conclusion The use of non-invasive stereotactic treatment of tachyarrhythmias has high potential in modern arrhythmology as an alternative ablation method. Abstract Figure. Macro- and microscopic results