Boosting Production in the Llanos Orientales Colombia Basin, with an Approach to the Usage of the Completion Fluid. A Recent Case Study

This arcticle highlights the importance of a systematic step change approach to the formulation of completion fluids in the Llanos Basin (LLAB), Colombia, when formation-freshwater is to be used as control - completion (C&C) fluid. The results demonstrate that the process used reduced the formation damage statistics from 41% of the wells drilled to only 16%, boosting production and establishing a best practice for future drilling and completion (D&C) campaigns in the region. An initial sample of 19 wells was considered to evaluate the damage caused by using formation-freshwater as C&C fluid. Formation-freshwater was selected only considering the fluid density (wellbore pressure), ignoring the negative effects it can have on formation damage. 41% of the wells were damaged, as evidenced by pressure build up. Some of the main damages on the pay-zone in an oil well are due to emulsion blocking, change in wettability, swelling and migration of clays, incompatibility of fluids, and scale formation. A detailed design of completion fluids has a positive influence over well productivity by mitigating formation damage before starting the production stage. The methodology used was aimed at designing the C&C fluid through a step-by-step approach, consisting of: 1) Laboratory tests supported with mineralogical data and oil and formation water properties and 2) Physical-chemical analysis of reservoir fluids and water for mixing purposes. The process involved testing different formulations and then their implementation in the field. The initial tests were conducted in a total of 5 wells in 4 fields. Changes were identified in the formulation to achieve optimal fluid design for each field and then the selected fluid was extended to a total of 24 wells. This was the first time a thoroughly designed completion fluid was used in the region. The results point towards the need to include surfactants, mutual solvents, and brines to substantially reduce formation damage. The application of new completion fluids enabled the operational teams to optimize the process by steps. The implementation of customized completion fluid reduced the formation damage as evidenced through productivity analyses and pressure build up tests. Only 16% of the wells presented formation damage. The process applied to reduce formation damage of the Llanos Basin led to a systematic approach for the analysis stage, which may be applied in other areas, where the utilization of formation-freshwater is an issue. The particularly short time frames and best practices derived from the learning curve of this case are worth to be shared with other operators.

Innovative Technologies Deliver Operational Objectives in a Multi-Well, Ultra-Deepwater, Managed Pressure Drilling and Completions Campaign

The deepwater development field in the western Gulf of Mexico (GoM) presents an array of complex challenges for ultra-deepwater drilling operations. The four well campaign was particularly challenging due to extreme water depths, remote location, well trajectory and a narrow pressure environment, 350-100 kpa (50-150 psi), for extended reservoir laterals. The authors highlight the use of innovative technology employed to drill and complete wells in the western GoM deployment, coupled with the first-ever use of controlled mud level (CML), managed pressure drilling technology in the Gulf of Mexico. The approach of selecting the fluid systems to achieve the objectives and the use of hydraulics modeling software with CML modeling capability in the design, planning and execution phases of the project allowed for fluid design optimization. The results were a successful drilling and completion campaign managing multiple fluids systems and operations on an ultra-deepwater, dual-activity drill ship in water depths more than 8,500 ft (2,591 m). The authors discuss the initial use of a low equivalent circulating density (ECD), flat-rheology synthetic based fluid (SBF) designed for narrow margin drilling applications and the transition to the deployment of a newly developed high-performance water-based mud (HPWBM) optimizing the operations to drill the intermediate intervals for final two wells. The authors also will discuss use of the reservoir drill-in fluid (RDF) and solids-free screen running fluids (SF-SRF), designed specifically for use in these open holes, gravel pack completions at hole angles upwards of 90°. Operational efficiencies derived from use of these fluids include ECD management, hole cleaning, directional performance, reduction in downhole losses, and the elimination of non-productive time (NPT) in a narrow margin environment with no loss of rate of penetration (ROP). Additional efficiencies include the seamless transition from derived from use of water-based fluids for drilling and completion phases. Use of the CML technology allowed for precise control of the hydrostatic pressure on wells that previously would not have been technically feasible to drill or complete. The novel use of the newly developed HPWBM on this campaign enabled reduced health, safety and environmental (HSE) exposure impact, increased tank and rig cleaning efficiency, and the elimination of a wellbore cleanout run since the entire well was drilled with only water-based fluids. The fluids were successfully employed in the four wells drilled and completed in a managed pressure environment utilizing CML technology.

Delivering Zonal Isolation between Reservoir Sublayers in Long, Horizontal 12 ¼-in. Hole Sections in Extended Reach Wells

Good cementing practices are required to achieve effective zonal isolation and provide long-term well integrity for uninterrupted safe production and subsequent abandonment. Zonal isolation can be attained by paying close attention to optimizing the drilling parameters, hole cleaning, fluid design, cement placement, and monitoring. In challenging extended reach wells in the UAE, different methods were employed to deliver progressive improvement in zonal isolation. Cementing the intermediate and production sections in the UAE field is challenging because of the highly deviated, long, open holes; use of nonaqueous fluids (NAFs); and the persistent problem of lost circulation. Compounding the problem are the multiple potential reservoirs; the pressure testing of the casing at high pressures after cement is set; and the change in downhole pressures and temperatures during production phases, which results in additional stresses. Hence, the mechanical properties for cement systems must be customized to withstand the downhole stresses. The requirement of spacer fluids with nonaqueous compatible properties adds complexity. Lessons learned from prior operations were applied sequentially to produce fit-for-purpose solutions in the UAE field. Standard cement practices were taken as a starting point, and subsequent changes were introduced to overcome specific challenges. These challenges included deeper 12 ¼-in. sections, which made it difficult to manage equivalent circulating densities (ECDs), and a stricter requirement of zonal isolation across sublayers in addition to required top of cement at surface. To satisfy these requirements, several measures were taken gradually: applying engineered trimodal blend systems to remain under ECD limits; pumping a lower-viscosity fluid ahead of the spacer; using NAF-compatible spacers for effective mud removal; employing flexible cement systems to withstand downhole stresses; and modeling the cement job with an advanced cement placement software to simulate displacement rates, bottomhole circulating temperatures, centralizer placement, mud removal and comply with a zero discharge policy that restricts the extra slurry volume to reach surface. To enhance conventional chemistry-based mud cleaning, an engineered scrubbing additive was included in the spacers with a microemulsion-based surfactant. The results of cement jobs were analyzed by playback in advanced evaluation software to verify the efficiency of the applied solutions. This continuous improvement response to changes in well design has resulted in a significant positive change in cement bond logs; a flexural attenuation measurement tool has been used to evaluate the lightweight slurry quality behind the casing, which has helped in enhancing the confidence level in well integrity in these challenging wells. The results highlight the benefit of developing engineering solutions that can be adapted to respond to radical changes in conditions or requirements.

Controlling Costs and NPT: An Economical Approach to Wellbore Strengthening Offshore Vietnam

There are many challenges while drilling highly inclined and depleted formations offshore Vietnam that result in various wellbore stability issues such as severe losses, stuck pipe, cavings, tight-hole and pack-offs. These issues may be independent of mud type and can occur when drilling with both oil/synthetic-based and water-based muds. These depleted sections typically consist of sandstones interbedded with claystone & siltstones. Traditionally, the wellbore strengthening fluids solution applied to drill through these sections with synthetic and water-based mud in Vietnam faced limited success. Wellbore strengthening (WBS) is a proven and effective solution especially for narrow-drilling margin and depleted formations. The basic concept of WBS relies on the creation and simultaneous plugging of small fractures with appropriate WBS material. The resulting elevated stress around the wellbore strengthens the borehole by creating an increased hoop stress that leads to an increase in near wellbore stresses. Proprietary modelling software can be used to calculate the pressure induced fracture apertures for wellbore strengthening applications and determine the optimum particle size range to bridge these fractures, allowing fluids to be designed to minimise wellbore instability. This design process was used to optimize material additives to effectively bridge fractures, for wellbore strengthening, and pore throat openings in porous/permeable formations for the prevention of seepage losses and differential sticking. A review of the application procedure identified the optimum method to apply the wellbore strengthening material which would minimise product consumption and reduce well costs. After extensive modelling simulations and testing, this fluid design was applied to drill two challenging wells in Vietnam. This paper presents the process of modelling, based on formation geo-mechanics information, customization and laboratory testing of the fluids design coupled with a successful and economical method of application in the field. Application of this process enabled the operator to drill through the depleted challenging sections with a maximum overbalance pressure of 3,200 psi, conduct logging and coring runs and complete the well at a lower cost and with zero fluids related non-productive time compared to previous wells.

Development Field First - Directionally Drilling Through Challenging Muderong Shale and Highly Depleted Reservoir Sand with HPWBM

Advancement in High Performance Water Based Mud (HPWBM) coupled with a deeper understanding of shale and chemical interaction has taken a leap in recent years enabling the drilling of challenging wells whilst replacing Synthetic Based Mud (SBM) as the preferred technical option. The exceptional inhibition properties, versatility to chemical manipulation and stability, as well as being an environmentally beneficial alternative to SBM, HPWBM has proven to be a robust solution for drilling the challenging Muderong shale and highly depleted reservoir sands in the field. Through a detailed field wide offset review focusing on wellbore stability and shale reactivity relationship observations, time dependent shale reactivity and an engineered bridging package was the basis of a successful fluid formulation and selection which then resulted in a flawless execution of the challenging well. Various testing of shale cuttings from the field paired with an offset review was key to understanding the extent of shale reactivity in relation to the type of shale being drilled and cause of shale instability in the area. These results were imperative in providing technical justification to utilise HPWBM for drilling through the Muderong shale. Applying detailed reservoir drilling fluid analysis to the overburden drilling fluids design and incorporating previous offset fluid design learnings, provided a robust and versatile drilling fluid system. This paper will review the steps undertaken to validate the selection of HPWBM over SBM through detailed analysis of wellbore stability, shale reactivity, permeability assessment, pore throat sizing and pore pressure transmission. It will present the misnomer of comingling the wellbore stability requirement, primarily mud weight, with shale reactivity in the field as well as the relation between the plateauing of shale reactivity curves to near well wellbore swelling. Extensive laboratory testing was performed to formulate and demonstrate the efficacy of the bridging package in addressing differential sticking, losses and wellbore strengthening in highly depleted sands. In addition, this paper will also present actual field results on stability of the fluid properties along with resultant torque and drag throughout drilling of a directional well with no requirement for lubricants. This paper should be of interest to all engineers and technologists who are involved in shale reactivity analysis, well design, drilling fluids design, selection and interaction as well as highly depleted reservoir sand drilling.

Engineering roles in Building with Nature interdisciplinary design

Building with Nature (BwN) infrastructure designs are characterised by disciplinary integration, non-linearity, diverse and fluid design requirements, and long-term time frames that balance the limitations of earth’s natural systems and the socio-technical systems created by humans. Differentiating roles in the engineering design process may offer strategies for better solutions. Four complementary engineering design roles were distinguished, namely: Specialists, System Integrators, Front-end Innovators, and Contextual Engineers. The key research question addressed in this paper asks, how can the introduction of engineering roles enhance interdisciplinary processes for BwN design? Three Building with Nature design workshops with international groups of students from multiple disciplines and various education levels provided the ideal context for investigating whether engineering roles enhance such interdisciplinary ways of working. Results indicate that the application of engineering roles in each of the three workshops indeed supported interdisciplinary design. A number of conditions for successful implementation within an authentic learning environment could be identified. The engineering roles sustain an early, divergent way of looking at the design problem and support the search for common ground across the diverse perspectives of the team members, each bringing different disciplinary backgrounds to the design table. The chapter closes with a discussion on the value of engineering design roles and their significance for the Building with Nature approach.

Tackling the Grand Challenge of Algorithmic Opacity Through Principled Robust Action

Organizations increasingly delegate agency to artificial intelligence. However, such systems can yield unintended negative effects as they may produce biases against users or reinforce social injustices. What pronounces them as a unique grand challenge, however, are not their potentially problematic outcomes but their fluid design. Machine learning algorithms are continuously evolving; as a result, their functioning frequently remains opaque to humans. In this article, we apply recent work on tackling grand challenges though robust action to assess the potential and obstacles of managing the challenge of algorithmic opacity. We stress that although this approach is fruitful, it can be gainfully complemented by a discussion regarding the accountability and legitimacy of solutions. In our discussion, we extend the robust action approach by linking it to a set of principles that can serve to evaluate organisational approaches of tackling grand challenges with respect to their ability to foster accountable outcomes under the intricate conditions of algorithmic opacity.

FUEL TAP: A SIMPLIFIED BREED AND BURN MSR

Breed-and-burn Molten Salt Reactors are an interesting option of reactor design that allow high fuel utilization while operating on an open fuel cycle. Such reactors usually require specialized codes in order to model its fuel cycle and the flowing fuel in an unmoderated core. In this work, we propose a design and perform a preliminary analysis of a homogeneous chloride salt single-fluid design. The fuel cycle is analyzed using the EQL0D tool in order to model reactor start-up and transition into an equilibrium state. Core simulation is performed using ATARI, an OpenFOAM-based multiphysics code developed at PSI. Results show that the core size for such a reactor is quite big and that it can be easily started with high-assay LEU. In addition, the core has been designed to promote a quasi-1D flow, opening the possibility of modeling the core with legacy codes in the future.