Unique 15kpsi Multistage Fracturing Liner System Delivers Solution to Overcome Tight Formation Challenges

Open hole Multistage Fracturing (MSF) systems have been deployed for treating open hole formations with multiple, high rate hydraulic fracturing stages while gaining efficiency during pumping operations unlike traditional plug-and-perf operations. One important challenge within the industry was availability of an open hole packer system that can overcome tough wellbore conditions during deployment and function as designed during the high rate high pressure stimulation operations. This paper will discuss the successful planning and deployment of one such system. For successful deployment of any open hole fracturing completion, one must first consider the environment that the system will be deployed into. Lateral length, open hole size, parent casing size and tubing stresses during fracturing and production all inclusively influence the need for a robust and reliable system. Other several important considerations to be deployed as a liner is the compatibility of the completion tools with the Liner deployment system, the robustness of being deployed into challenging open hole conditions where capability of high circulating rates and rotation become mandatory to get the bottom hole assembly (BHA) to its final setting depth. Last but not least, in order to achieve successful stimulation, each component of the system after overcoming all the deployment obstacles should function as designed withstanding treating differentials as high as 15kpsi, while simultaneously accommodating induced axial loads caused by these high-pressure treatments. The development and testing of individual components of the system was done keeping in mind wellbore instability and obstacles the completion will have to overcome during deployment. The field execution was planned with close collaboration with the operator and other key services that were involved for drilling the well. Real-time monitoring of the well allowed for simultaneous swift implementation of changes required on tool activation pressures, identification of hazards and mitigation plan to overcome challenges in order to execute the job successfully. It is worth mentioning that the successful deployment of this system represents the first use of additive manufacturing in high pressure, hydraulic set open hole packers. This technology allowed overcoming the barriers of challenges associated with deploying open hole completion in tight challenging formations that would otherwise have limited deployment capabilities.

Cutting Re-injection CRI Uncertainty and Risk Assessment

It is the responsibility of oil and gas operators to recycle or dispose of drilling cuttings in a safe and environmentally friendly manner. Environmental regulations are very strict in establishing that green operations and cutting re-injection be as clean and friendly to environment as possible despite the associated challenges and cost. It is the preferred technique by the majority of international companies. Cutting re-Injection operations include grinding down the drilling cutting to small particle sizes and mixing them with a water-based fluid (mud, water, gel) to form a slurry. The slurry is then pumped under high pressure into a disposal formation where fractures can be initiated and propagated. Existing wells can be used as appropriate by targeting watered-out formations far from hydrocarbon- bearing zones; sometimes operators drill new wells purely for cutting reinjection purposes. The main sources of uncertainty include reservoir heterogeneity, permeability, pore throat size and fluid leakoff rates into the formation. The optimum scenario is to pump the cutting re-injection slurry into a very high permeability formation where screening out, plugging or well packing is unlikely, assuming solids are suspended and are completely lost into the formation. This scenario can only be feasible if the formation pore throat size is much larger than the solid size. This paper presents how to conduct risk assessments for all possible scenarios considering all sources of uncertainties. The paper also shows that under some circumstances it is better to pump the cutting slurry into a very tight formation, such as shale (closed system), than a permeable formation with a high degree of uncertainty where screenout potential risk is most likely.

Swarm Of Autonomous Underwater Vehicles – Preliminary Results Of The Control System

A swarm of autonomous underwater vehicles can be a valuable alternative for fully equipped and very expensive super-vehicles. A distributed system of tightly cooperating vehicles can be cheaper, simpler in maintenance, more reliable, more flexible and universal than traditional single-vehicle systems. However, keeping a tight formation of underwater vehicles in the condition of the sea current, unclear environment, and rare inter-vehicle communication is a very challenging problem, which requires an effective vehicle control system. The paper proposes a solution to the above-mentioned problem, which is based on neuro-evolution. Moreover, the paper also presents the first results of the proposed system.

The Effects of Gas Mixture Composition on the Mass Transfer and Individual Diffusion Coefficient in CH4-CO2-Light Oil Systems

Limited CO2 resources considerably narrow down the field application of CO2 EOR for improving oil recovery in tight formation. Considering that CH4 and CO2 have similar EOR mechanisms, CH4, as a by-product of produced oil, is a relatively cost-efficient agent to be injected into the tight formation with CO2. In this work, experimental and mathematical methods are proposed to probe the effect of CH4 composition on the mass transfer between a CO2-CH4 gas mixture and crude oil collected from a tight oil reservoir. Experimentally, the pressure-decay tests for different CH4-CO2-light oil systems are conducted at a constant temperature in a pressure / volume / temperature (PVT) setup. Also, the gas mixtures’ compositions before and after the experiments are analyzed with gas chromatography to investigate the mass transfer of different components. Theoretically, mathematical formulations are developed to describe the mass transfer between the gas mixture and light oil based on translated Peng Robinson equation of state (PR-EOS), a real gas equation, and one-dimensional convection-diffusion equations. The individual diffusion coefficients of CH4 and CO2 as well as the concentrations distribution can be obtained by minimizing the deviation between the calculated pressure and the measured ones. The results indicate that the higher the content of CO2 in the initial gas phase, the faster the pressure drops are and less time it takes for the oil and gas phases to reach a stable pressure, which implies a high mass transfer rate with an increase in CO2 composition. In particular, the diffusion coefficient of CO2 is found to be about 2 times larger than that of CH4 the same composition condition. However, it is noted that the individual diffusion coefficients of CH4 or CO2 are not constants. A high molar fraction in the initial gas sample will lead to a large diffusion coefficient in different CH4-CO2-light oil systems.