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Summary Mitigating excessive water production becomes a major issue in fractured carbonate reservoirs. Finding a suitable in-depth water control strategy to be applied in highly heterogeneous mature field by Polymer/gel injections is the key objective of the study presented in this paper. Targeted field suffers from severe conformance problems due to strong heterogeneities, fractures, vugs, with a water cut around 92%. The objective was to optimize a robust gel system that could be placed in-depth for a sustainable effect. A laboratory study has been performed to design a chemical gel system for in-depth conformance at the injector or near-well treatment at the producer. This requires optimization of chemical formulation, coreflood testing and overall behavior in reservoir conditions. Experimental program included gel rheology measurements, bottle tests for gelation time and gel stability assessments. Five gel systems were studied. Influence of polymer and crosslinker concentrations and brine composition was investigated to formulate and optimize gel properties. In a second step, coreflooding experiments conducted in fractured cores aimed at evaluating gelant injectivity, gel breakthrough pressure, permeability reduction and pore volume reduction induced by the gel. Viscosity measurements and gelation tests qualified two systems among the five tested ones. Both systems had a gelant viscosity meeting the maximum requirement of 200cP and lead to strong gels after a few days. Accelerated ageing tests were performed at 73, 80 and 90°C to mimic 5 years of ageing time at reservoir temperature (50°C). They confirmed an excellent gel stability for one system (called “Gelix”) achieving the target consistency whatever the temperature. Six corefloods showed that in-situ performance of Gelix was above those of the other systems. Gelix induces high gel parting pressure (70 bar/ft) and a residual permeability reduction (>500 000 ) in highly fractured core, making it suitable to block fractures and/or high permeability streaks for in-depth water control. Gelix system was thus qualified as the best gel to be used in this field. Finally, in order to protect the oil-bearing matrix, hybrid injection strategy was designed, using alternate slugs of microgel and Gelix. Such strategy can be applied in bullhead mode, optimizing gel placement in the fracture network, while minimizing the risk of damage by protecting matrix from gel leak-off. The paper describes the workflow to qualify in-depth water control and conformance products for fractured carbonate reservoirs. It highlights the benefits of a hybrid approach to protect oil bearing matrix while blocking the high-permeability streaks.

Reutlingen. Aus der Geschichte einer Stadt. Hrsg. Paul Schwarz, Heinz Dieter Schmid-Reutlingen: Oertel & Spörer. (1973). 267 S. Ill. DM 64.-.

Abstract Seafloor currents, including episodic sediment-laden turbidity flows and more sustained thermohaline-driven bottom currents, control the ultimate fate of sediment, carbon and pollutants in the deep-sea. Collectively, these currents form the largest sediment accumulations on Earth, from which past climate records are reconstructed. A long-standing view has been that thermohaline-driven bottom currents are persistent and stable; however, a paucity of direct near-seabed monitoring means this remains untested at field-scale. Here, using the most spatially-extensive and long-duration (4-yrs) monitoring of bottom currents at 34 deep-sea instrumented moorings, we show that such currents are far from steady and continuous. Bottom currents instead show dynamic, spatial variability in velocity and direction over tidal and seasonal timescales, being strongly influenced by local seabed morphology. Prior lower resolution monitoring has underestimated this spatio-temporal variability of bottom currents; hence our results highlight a need for near-bed measurements to more robustly quantify deep-sea sediment, carbon and pollutant fluxes.

Pretrained models for "End-to-end AI Framework for Hyperparameter Optimization, Model Training, and Interpretable Inference for Molecules and Crystals" paper submitted to MLST journal.

Abstract During the completion phase of four unconventional wells in the United Arab Emirates (UAE), a detailed engineering approach enabled overcoming challenges presented by the extreme conditions of pressure, temperature, and sour environment across long horizontal sections to successfully carry out cleanout activities. The methods implemented to address those conditions prioritized personnel safety and asset integrity. The unconventional wells in this campaign were characterized by a reservoir pressure of approximately 13,000 psi and a bottomhole temperature of approximately 325°F. Gas was expected as reservoir fluid. The environment was sour, with 5% mol of H2S and 5% mol of CO2. After fracturing, the shut-in pressure was approximately 8,000 psi. Those conditions triggered a new engineering approach to design a customized coiled tubing (CT) pipe that could reach depths of 20,700 ft and perform efficient cleanouts. Other considerations included the selection of the appropriate pressure control equipment (PCE), downhole tools, and intervention fluids that could withstand the harsh working conditions. The wells were completed with 5 1/2-in. fracturing strings; horizontal sections ranged from 5,000 to 8,200 ft. Each of the 95 fracturing stages was isolated by dissolvable plugs. The CT pipe design considered well trajectories, working pressures, and downhole environment. The highly engineered 22,000 ft, 2 3/8-in. CT string was manufactured with quench and tempered (Q&T) material with yield strength of 110,000 psi. A custom-fit CT string integrity program was implemented to ensure safe intervention in high-pressure sour environment. Pipe life was then monitored in real time using magnetic flux leakage. Downhole tools (CT connector and check valves) and the PCE stack were designed to hold pressures up to 15,000 psi. The PCE configuration was thoroughly reviewed, and since the wellhead stack exhibited a maximum height of approximately 120 ft, a stack stress analysis through finite-element modeling software was conducted to validate structure stability, to confirm forces and bending moments remained within safe working limits, and to determine the optimal setting for guy wires. Job execution highlighted challenges linked to the high-pressure cycling and the need to optimize the number of achievable sweeps in the horizontal section. Well trajectories also proved challenging for the cleanout, with solids accumulation in specific intervals. This operation, the first of its kind in the country for the operator, yielded lessons for design considerations and the execution process and recommendations for CT intervention in similar working environments. It also confirms that 110,000-psi yield strength Q&T CT strings can be safely deployed in a high-pressure sour environment by implementing proper risk mitigation strategies.

Summary Inversion velocity analysis (IVA) alternates between migration and tomography steps. It uses the pseudo-inverse of the extended Born operator to compute an improved extended reflectivity in comparison to migration velocity analysis (MVA) based on the adjoint of the extended Born operator. One important feature of the pseudo-inverse formula is that it is defined such that the migration Hessian is approximately diagonal. In this work, we report our first evaluation of the tomographic Hessian of IVA for the estimation of the background velocity model. We apply the second-order adjoint-state method to obtain the action of the tomographic Hessian on a vector. Then, improved update directions are obtained by computing approximately the action of the inverse of the tomographic Hessian on the descent direction. One numerical example demonstrates the potential of the tomographic Hessian-based IVA.

Abstract Al-Khalij is a complex carbonate oil field located off the coast of Qatar that has been under production since 1997. Its development is based on long horizontal producer wells crossing several layers and equipped with Electrical Submersible Pumps (ESPs) as artificial lift method. Water injectors are used for pressure support and sweep efficiency. Despite an intensive open hole acquisition program, well behavior monitoring remains challenging due to the reservoir complexity and uncertain water production mechanism. Moreover, wells are mostly equipped with Dual ESPs, making cased hole acquisitions (such as spinner logs or saturation logs) not applicable. In order to tackle the observed continuous oil production decline, a new strategy has been implemented since 2007: installing Flow Control Valves (FCVs) as part of the completion strings. Since then, 26 producer wells have been equipped with up to 3 FCVs each. These FCVs are hydraulically controlled from surface and packers are used to isolate the completed zones. As FCVs appeared to be reliable (success ratio close to 100%), they have, since 2011, been systematically installed on new wells or during work-overs for ESP replacements. The expected reservoir monitoring benefits were to better understand the well behavior of long horizontal drains with commingled production and differential depletion and to have a partial substitute for spinner log acquisition. The expected reservoir-management benefits were to have more flexibility for controlling the water production and balancing the liquid withdrawal from the reservoir and thus limit interferences between wells. In the end, the added value from FCV installation on Al-Khalij wells was above expectations. Indeed, in addition to the previously mentioned benefits, the flexibility brought by FCVs allowed reservoir engineers to be more aggressive on perforation strategy and drain extensions for appraising new areas. Consequently, new upsides were identified leading to additional infill wells in the southern part of the field. After a continuous decline observed since 2006, Al Khalij oil production has now been stabilized and the overall water cut of the field has slightly decreased. Following this evaluation the field reserves have been reevaluated and new projects are still to come …

El objetivo de esta investigación fue caracterizar la demanda de servicios en salud mental, de la población afiliada a una aseguradora en salud en Colombia durante el año 2012. Se realizó un estudio descriptivo retrospectivo de corte transversal con base en información de 52.624 afiliados y 463.522 atenciones en 16 ciudades. Se determinaron frecuencias por servicio y grupo diagnóstico, y se compararon proporciones mediante la prueba estadística Chi cuadrado. Se encontró que las mujeres tuvieron mayor uso de servicios a partir de los 15 años. El trastorno mental registró el mayor número de atenciones. El abuso y dependencia al alcohol y a sustancias psicoactivas predominaron en los hombres, mientras que intento de suicidio, lesiones autoinfligidas y violencias, en las mujeres.

Abstract The ability to access and share valid and up-to-date technical information is a key element of our operational efficiency with the follow-up of our projects and operations. This will have a critical impact in case of incidents and/or crisis situations, as this could happen in sensitive area like Nigeria. In case of a major crisis, we must be able to restore access to the identified critical facilities stored in GIS datasets within a time limit of 4 to 8 hours!