Maximizing Stimulation Efficiencies in Offshore Multistage Completions, Black Sea, Romania

This paper presents an analysis of the stimulation treatment design and operational efficiencies in the Black Sea. In greater detail, the paper focuses on how the stimulation design and each operational step has been optimized to save time, money and ensure an HSE driven completion methodology. An analysis was performed on the stimulation design and implementation approach looking at its evolution through a knowledge building and lesson learning process. The principal goal was to determine the most economical way to stimulate an offshore well without making any concessions to the reservoirs’ production or ultimate recovery. From the basics of well and frac design to completion optimization, effort was applied in analyzing ball launching procedures, frac spacing, logistical arrangements on the stimulation vessel and all other areas where there was potential to make improvements. Ultimately, an analysis of fluid displacements during flush was performed and deductions inferred. Past stimulation treatments were analyzed in an effort of better understanding the advantages and disadvantages in terms of production output of the wells. Similarly, an analysis of the completion approach and operational efficiencies showed the ability of pumping three stimulation stages a day. Considering that horizontal wells in the area are usually completed in six stages, a stimulation campaign would effectively be completed in 2 pumping days, 4 days total if no weather or operational delays are faced. Further improvements of this approach have been implemented in 2021 when six stimulation stages have been pumped in a single vessel ride. Applying the ball drop procedure offshore showed optimal results, as it is efficient in reducing downtime in between fracturing stages and in achieving proper isolation between stimulation zones. Likewise, with over flush being a concern throughout most of the stimulation population, certain cases in the Black Sea showed that over flushing did not adversely affect production of the wells with the production exhibiting ~15% above expected production rates post stimulation. In conclusion, the authors believe that the operational efficiencies achieved in the Black Sea are transposable in other offshore environments and successful cost cutting can be achieved by sound engineering and logistical decisions. The approach and results are beneficial in understanding where the economics are positively impacted in multistage stimulation treatments in the offshore environments, hence ultimately improving the rate of return.

From initial treatment design to final disposal of chelating agents: a review of corrosion and degradation mechanisms

In this review, we discuss how chelating agents and their products can cause corrosion and how it goes through the oilfield cycle including thermal, photo, and biodegradation.

The impact of psychological theory on the treatment of Attention Deficit Hyperactivity Disorder (ADHD) in adults: A scoping review

Psychological theory and interpretation of research are key elements influencing clinical treatment development and design in Attention Deficit Hyperactivity Disorder (ADHD). Research-based treatment recommendations primarily support Cognitive Behavioural Therapy (CBT), an extension of the cognitive behavioural theory, which promotes a deficit-focused characterisation of ADHD and prioritises symptom reduction and cognitive control of self-regulation as treatment outcomes. A wide variety of approaches have developed to improve ADHD outcomes in adults, and this review aimed to map the theoretical foundations of treatment design to understand their impact. A scoping review and analysis were performed on 221 documents to compare the theoretical influences in research, treatment approach, and theoretical citations. Results showed that despite variation in the application, current treatments characterise ADHD from a single paradigm of cognitive behavioural theory. A single theoretical perspective is limiting research for effective treatments for ADHD to address ongoing issues such as accommodating context variability and heterogeneity. Research into alternative theoretical characterisations of ADHD is recommended to provide treatment design opportunities to better understand and address symptoms.

Dolomite Stimulation with Retarded Acids

Globally, dolomite formations are important reservoirs for oil and gas. Acid stimulation is commonly used to extend the life of carbonate reservoirs, and a good understanding of the fluid performance is essential for effective treatment design. Three acids, hydrochloric acid (HCl), emulsified HCl, and a single-phase retarded acid based on HCl, were assessed for their ability to create wormholes in Silurian dolomite under laboratory conditions using a standard core flow experiment. Select cores were imaged by X-ray computed tomography to visualize the wormhole morphology. Similar experiments in Indiana limestone was used as a control. The core flow experiments showed that the pore volume to break-through (PVbt) values for the retarded acids in Indiana limestone were less sensitive to changes in temperature overall than unmodified HCl. For Silurian dolomite though, the opposite is observed. HCl has uniformly high PVbt values at lower (200 °F) and higher (325 °F). The emulsified acid and the single-phase retarded acid are more efficient than HCl, but the difference is smaller at 325 °F. Core images revealed that all three fluids had some degree of wormhole branching at 200 °F and much less branching at 325 °F. By visual inspection, the single-phase retarded acid has less ramification than HCl and the emulsified acid. Overall, the results show that retarded acids should make effective stimulation fluids for dolomite reservoirs.

Uncertainty in Wastewater Treatment Design and Operation

Uncertainty in Wastewater Treatment Design and Operation aims to facilitate the transition of the wastewater profession to the probabilistic use of simulators with the associated benefits of being better able to take advantage of opportunities and manage risk. There is a paradigm shift taking place in the design and operation of treatment plants in the water industry. The market is currently in transition to use modelling and simulation while still using conventional heuristic guidelines (safety factors). Key reasons for transition include: wastewater treatment simulation software advancements; stricter effluent requirements that cannot be designed for using traditional approaches, and increased pressure for more efficient designs (including energy efficiency, greenhouse gas emission control). There is increasing consensus among wastewater professionals that the performance of plants and the predictive power of their models (degree of uncertainty) is a critical component of plant design and operation. However, models and simulators used by designers and operators do not incorporate methods for the evaluation of uncertainty associated with each design. Thus, engineers often combine safety factors with simulation results in an arbitrary way based on designer ‘experience’. Furthermore, there is not an accepted methodology (outside modelling) that translates uncertainty to assumed opportunity or risk and how it is distributed among consultants/contractors and owners. Uncertainty in Wastewater Treatment Design and Operation documents how uncertainty, opportunity and risk are currently handled in the wastewater treatment practice by consultants, utilities and regulators. The book provides a useful set of terms and definitions relating to uncertainty and promotes an understanding of the issues and terms involved. It identifies the sources of uncertainty in different project phases and presents a critical review of the available methods. Real-world examples are selected to illustrate where and when sources of uncertainty are introduced and how models are implemented and used in design projects and in operational optimisation. Uncertainty in Wastewater Treatment Design and Operation defines the developments required to provide improved procedures and tools to implement uncertainty and risk evaluations in projects. It is a vital reference for utilities, regulators, consultants, and trained management dealing with certainty, opportunity and risk in wastewater treatment. ISBN: 9781780401027 (Paperback) ISBN: 9781780401034 (eBook) ISBN: 9781789062601 (ePub)