Jet-type perforate-wash-cement (P/W/C) is a relatively new well plugging technique that is more cost effective than the traditional casing milling method. ConocoPhillips has extensively used this technique in the Greater Ekofisk Area (GEA) over the last 10 years. In this method, Tubing Conveyed Perforating (TCP) guns perforate casing in the target interval before the zone is washed and a cross-sectional cement plug is installed using a specialized Bottom Hole Assembly (BHA). The BHA has nozzles in respective zones to separately spray wash fluid and cement during the operation. Tool translational (up and down movement) and rotational speeds, nozzle diameter, number of nozzles, nozzle angle, mud and cement properties, flow rates and nozzle pressure drop are the key governing parameters. In 2014, ConocoPhillips Norway launched a project to improve quality of wash and cement processes and since 2016 utilized Computational Fluid Dynamics (CFD) for parametric optimization. The analysis significantly enhanced understanding of the fundamental processes involved, enabling improvement of the existing tool and processes. The focus of this paper is on how BHA rotational speed, nozzle diameter, and nozzle angle influence wash process efficiency. Deeper insight from CFD analysis on the influence of these parameters on the wash process is discussed in more detail in this paper. Updated wash and cement procedures and parameter values were introduced in 2017 based on CFD modeling and detailed in a best practice document. To date approximately 200 successful operations have been performed as per the best practice.

Perforate-Wash-Cement (P/W/C) is a well plugging technique extensively used by ConocoPhillips in the Greater Ekofisk Area over the last ten years. In Jet-type P/W/C, Tubing Conveyed Perforating (TCP) guns perforate casing in the target interval before the zone is washed and a cross-sectional cement plug is installed using a specialized Bottom Hole Assembly (BHA). The goal is to maximize the cement plug quality through optimizing the BHA and operational process parameters within constraints imposed by the operating conditions. This paper describes application of Computational Fluid Dynamics (CFD) to achieve this objective. CFD is well suited for modeling wash and cement processes including the associated non-Newtonian fluids. A CFD model of these processes employs unsteady multiphase Reynolds Averaged Navier Stokes (RANS) based Volume of Fluid (VOF) approach with a Shear Stress Transport (SST) K-omega turbulence model. BHA translation and rotation are simulated using moving deforming-layering mesh with interface approach. Physical properties of non-Newtonian fluids selected are based on in-situ conditions and derived via lab tests. CFD-specific considerations such as domain size, turbulence model, mesh type and size, and computational timestep are discussed in this paper. The magnitude and duration of the jet-induced "pressure pulse" in the annular space between the formation wall and the casing are a key to efficient displacement during the wash and cementing processes. Displacement efficiency, in terms of the percentage of mud or cement in a control volume as a function of time, depends on perforation size and density, nozzle size/number, flow rate, fluid properties, as the ROP/BHA pulling speed and tool RPM. Key findings from a parametric study to optimize these parameters are presented. To validate CFD nozzle flow predictions and to rule out potential for false results due to cavitation, laboratory tests were performed under pressurized conditions. A comparison of results from CFD simulations using traditional versus optimized parameters are presented, demonstrating significant efficiency improvement achieved. The study initially focused on North Sea application. Encouraged by substantial improvement in process efficiency through parametric optimization, the technique was extended to UK operations and is planned for the Bayu-Undan field. Cementing simulation results for Bayu-Undan specific well configurations are presented, showing how CFD modeling helped reveal less than ideal cementing efficiency. Ultimately, this work provides significant time savings and quality improvement for P&A projects while maintaining a high safety standard.

The economic success of many drilling operations depends on the availability and reliability of real-time information about the drilling process. Mud pulse telemetry is currently the most common method of transmitting measurement-while-drilling (MWD) and logging-while-drilling (LWD) data. Advances in downhole sensing for drilling optimization and formation evaluation are placing heavy demands on telemetry systems to provide fast and reliable data rates from greater depths. However, solid particle erosion poses a significant problem for telemetry tools, where solid particle (such as sand) impingement could damage the tool string and shorten the service life of the tools. Therefore, a comprehensive investigation on erosion of mud pulse telemetry tools consisting of numerical simulation and field tests is often required to optimize the tool design. In the field, many factors can influence telemetry tool erosion such as material properties, sand size, geometry, flow velocity, operating pressure, and turbulence. These factors interact with each other, making the experimental study of all influencing parameters very challenging and time-consuming. In this work, computational fluid dynamics (CFD) simulations were used to study the effect of several parameters on the erosion rate, even in complex geometries where setting up an experimental study is difficult. The erosion rate was determined using the widely used Oka erosion model. Parameter studies were then performed to find the influence of flow rate and sand concentration on the erosion rate. Simulation was also performed to support the deployment of new engineered materials. For model validation, simulation results were compared with erosion patterns from field tests, showing good agreement between field observations and simulation results. Based on findings from the parameter studies, a formula of key performance indication (KPI) parameter was developed to evaluate the erosion performance of the mud pulse telemetry tools deployed in the field. After completing the field experiments, 3D laser scans of the deployed tools with different materials were performed. In addition, KPI values were calculated based on the scanning results to evaluate the actual erosion performance. Evaluation revealed that the new engineered alloy was eight times more erosion-resistant than stainless steel, which was consistent with the CFD simulation results. The results of this study indicate that CFD simulation provided an alternate way to predict solid particle erosion on logging tools in downhole environments. By using the high-fidelity erosion model, the tool erosion rate could be accurately predicted. Based on this conclusion, the erosion risk can be mitigated by providing guidance on repair and maintenance intervals and planning the drilling process to avoid premature tool failures. This approach will eventually improve the reliability and safety of downhole tool and reduce non-productive time (NPT) and costs.

In spite of the sand control/management techniques implemented down-hole, fine sand (< 50-75 microns) often may find its way into the piping components of onshore, offshore, and subsea facilities causing erosion/wear and subsequent pipeline integrity issues. Existing erosion models (both CFD-based and correlations) widely used in the industry have been reasonably benchmarked with erosion due to sand particles that are greater than 100-150 microns and the predictions are within ±100% of observations even in single-phase carrier (liquid or gas) flows. Although there is only a limited set of the fines erosion data (both lab and field), there is a considerable mismatch between the data and what the models predict even when the fines (< 50 microns) are carried in single-phase (let alone multiphase) fluid flow. Also, current industry practice is to assume that the low liquid content of gas stream reduces fines erosion by forming a protective film on the pipe wall although there is no clear understanding on what fraction of the liquid content (a) gets atomized into droplets (that may or may not wet the fine particles) in the gas stream and (b) wets the pipe wall. Even the development and validation efforts of the correlations for fine particle-pipe wall interaction leading to a single erosion event (let alone CFD-based erosion simulation) are still at their infancy. Several renowned erosion research groups around the world have been working on addressing the afore-said gaps. New fines erosion experiments were conducted in a 4" flow facility that consists of several piping components (orifice plates, elbows, and tees) that were connected in series and pipe wall thickness loss due to erosion was measured using a standard ultrasonic method. This paper elucidates the effect of (a) interaction of piping components connected in series (in-plane and out-of-plane) and (b) effect of low liquid loading in gas on fines erosion, scaleup to field conditions, and provides some directions for future efforts needed on this topic that are critical to the safe and efficient operation of oil-gas producing/processing facilities.