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Collaborating Authors
Completion Installation and Operations
Thermal Wellbore Strengthening: System Design, Testing, and Modeling
Hoxha, Besmir Buranaj (The University of Texas at Austin) | Incedalip, Oguz (The University of Texas at Austin) | Vajargah, Ali Karimi (The University of Texas at Austin) | Hale, Arthur (The University of Texas at Austin) | Oort, Eric van (The University of Texas at Austin)
Abstract Drilling through depleted zones in offshore deepwater prospects is becoming more common with ongoing production and field maturation, especially when deeper-lying, virgin-pressured reservoirs are explored and produced in later stages of field development. Some of the challenges associated with these depleted zones include severe mud loss and associated borehole problems, as well as troublesome cementing and poor zonal isolation. Artificially strengthening the wellbore is now becoming of crucial importance in order to successfully drill and cement deepwater wells in mature fields and any other wells with narrow drilling margins. In this paper, we introduce an innovative thermal wellbore strengthening (TWBS) technique to elevate the tangential stress (also known as the hoop stress) near the wellbore, and consequently increase the fracture gradient. A "thermal fluid," consisting of a carrier mud with heat-releasing ("exothermic") coated particles, has been designed to target depleted zones and release heat at exactly the right time to increase near-wellbore thermal stress, which directly elevates the near-wellbore tangential stress and in turn elevates the effective fracture gradient. Ultimately, this lowers the risk of lost circulation and improves the chance of successfully cementing and achieving zonal isolation. For instance, a TWBS treatment can be executed as an integral part of the cement job by using it in an extended spacer train for mud displacement, pumped directly prior to cement placement. The coated exothermic particles were designed such that they could release their "payload" via an extended time-release mechanism, to ensure that the heat release reaches the appropriate target location in the wellbore at the right time. The chemical systems, which are based on dissolving various hygroscopic salts in water, were tested and developed to heat up the wellbore and increase temperature up to 100°C. This will potentially elevate the fracture gradient by several hundred psi, depending on formation properties. Details regarding the formulation and testing of the non-coated, coated particles, and the carrier fluid are discussed; as well as considerations for TWBS field application. In addition, a new computational heat transfer model was developed to calculate the temperature distribution within the rock formation and within the drillstring/work string and wellbore annulus, for a formation contacted by a fluid with particles that react in exothermic fashion. The new model calculates the transient temperature distribution, increase in near-wellbore stress, and fracture gradient for a given amount of heat generation by the fluid and temperature increase in the rock. It can assist with well design aspects of the proposed thermal wellbore strengthening technique, and is particularly helpful in estimating the downhole temperature variations and assessing its implications prior to job execution. Details of the model and results of several typical simulations are given herein.
- Geology > Mineral (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock (0.69)
- North America > United States > Gulf of Mexico > Central GOM > East Gulf Coast Tertiary Basin > Mississippi Canyon > Block 851 (0.99)
- North America > United States > Gulf of Mexico > Central GOM > East Gulf Coast Tertiary Basin > Mississippi Canyon > Block 850 (0.99)
- North America > United States > Gulf of Mexico > Central GOM > East Gulf Coast Tertiary Basin > Mississippi Canyon > Block 808 (0.99)
- (5 more...)
Abstract Three-dimensional (3D) finite element analysis (FEA)-based shock software is the next step in downhole shock modeling. This software uses a finite element and a fluid tool that simulates gun behavior on gun strings and adjoining tools, including perforation and subsequent stress conditions. By examining temporal stress predictions at element locations, failures can be estimated based on these numbers. On a recent perforating operation, there was an undesired event that resulted in a collapse of the spacer section within the perforating string. The event flattened spacers, but did not ruptured them, resulting in not damage to other sections. This event highlights how localized dynamic forces could be over looked in the present 1D industry dynamic modeling software. As part of the planning process, the current industry standard shock software was used to simulate the string and predict the likelihood of failure. The models showed no failure flags; additionally, post-operation models did not predict the downhole events that occurred. As part of the investigation into the events, this modeling shock software was used to provide a more detailed model of the event. These models provide a full 3D representation of the string and allow a much more detailed understanding of the pressures and stresses during the perforating event. The models clearly showed the string design was not optimized for the localized dynamic event and there was a risk of collapse. Pressures were plotted as a function of time at locations on the outside of the spacers, safety spacer, and loaded guns. The results showed pressures outside the spacers, which exceeded static threshold values and lasted for extended durations. Other regions, such as the safety spacer, did not show this effect at above static threshold magnitudes. As well as being able to reproduce the collapse event , work was taken a step further to examine mitigation designs that could be used to help prevent these types of issues. It was possible to test several of these designs using the 3D FEA-based shock software to validate their functionality.
- North America > United States (0.29)
- Asia > Middle East (0.29)
Abstract All perforating operations cause some debris. Perforating debris can damage surface equipment and completion tools and negatively impact production. In high-pressure deepwater wells, minimizing debris becomes more important because costs associated with debris accumulation might impact sensitive completion equipment or might not be realized until later in a well's life. This necessitates a new low-debris perforating system designed to significantly reduce debris associated with high-shot-density big-hole charges. Past solutions at low-shot densities have involved introducing materials into the perforator to retain debris. The close proximity of these materials to energetic components can introduce strong shock waves between individual charge detonation events. This phenomenon has an undesirable effect on perforator performance and should be minimized without compromising debris retention. Traditional gun designs are based on a trial-and-error approach, using very limited post-testing measurements as design verification tools. The extremely complicated interactions among different components of the gun during a test cannot be observed experimentally, and the detailed physical process is not well understood. Therefore, numerical models have been developed to simulate the detailed dynamic responses of gun systems subjected to multiple shaped-charge detonations. This paper describes the coupling of hydrocode-based three-dimensional (3D) numerical models with FEA and full- scale surface testing. High-fidelity modeling is employed to capture the dynamic response of the materials under shock loading. The model is then used to investigate shock wave interference among the major components of the gun system. The underlying mechanics dominating the gun performance are identified. Consequently, considerable insight is obtained into gun system design for effective shock wave mitigation without compromising low-debris characteristics Investigations are performed for the original baseline design and a modified design based on numerical simulation results. Numerical and experimental results are presented for both designs. By comparison, the modified design outperforms the baseline design, as predicted by the numerical model, thereby validating the numerical model and providing greater confidence to the design cycle. Numerical simulations combined with the traditional experiments facilitate effective decision making, thus making the overall design cycle much more efficient.
Abstract Mature fields provide a good opportunity for oil producers because many of these fields contain reserves that can be recovered economically with a representative return on investment (ROI). Optimal production from perforated zones is always the goal, however minimizing /preventing formation damage, during a perforation event, can present challenges. This paper presents a case study in which an operator utilized a holistic aproach of a gun hanger in conjunction with artificial lift perforating solution to address formation fluid compatibility challenges while optimizing the perforations and perforation tunnel cleanup. This solution incorporated an advanced technical design with mechanical hardware. By designing a perforating solution using both static underbalance (UB) and a dynamic underbalance (DUB) technique to achieve oil production with minimal formation/skin damage and marrying this solution with gun hanger technology in an artificial lift completion, has resulted in oil production exceeding the operator's expectations. Technology advancements have provided renewed opportunities for hydrocarbon production from operator wells in mature fields. One used advancement includes application of a surging effect that uses an atmospheric chamber and creates Dynamic Under Balance immediately after a perforation event. The surge chamber creates an instantaneous in-situ negative pressure in the wellbore that provides a localized differential pressure that cleans the perforations (Haggerty et al. 2012). This helps improve the well inflow conditions and effectively reduces the formation damage normally generated by the perforation event (Poveda et al. 2013). By addressing formation fluid compatibility challenges, one could reduce the formation damage normally generated by the kill fluid introduced in the shoot and pull operation with tubing-conveyed perforating (TCP) systems. To acheve this, another design advancement is to use an electronic firing head (EFH) that can be programmed for a wide range of applications with different actuation times (up to 18 days). This EFH can be reset up to 15 times without locking the electronic system. The perforating gun string can be set on depth using an automatic-release gun hanger (ARGH) system. The ARGH helps to position the perforating string, detached from the completion string (ESP) to avoid shock loads from the perforating event interfering with ESP completion. The ESP is electrically tested while running in the well with the production pipe and electric cable. Once on depth, the operational pump test is conducted while evacuating the well-control fluid. This provides the designed static Under Balance as the initial condition for firing the perforating guns, which induces the interval oil production. The ARGH hydraulic system provides sufficient time for all designed effects in the formation. The purpose is to minimize the formation damage and provide optimized production. The well can be put on production at the end of the sequence steps designed with the ESP because the well is prepared in advance. This can help save up to 2 days of completion setup time in a pipe-conveyed perforating operation with the fluid change and the consequent formation damage. The complex processes involved in these operations are carefully simulated with industry tested and proprietary software programs. These programs help to confirm the desired effects can be achieved in production intervals to obtain the best oil production in optimal conditions. The simulations also account for the physical effects on the ESP, pressure and temperature sensors, and casing or liner installed in the well.
- Well Completion > Completion Installation and Operations > Perforating (1.00)
- Production and Well Operations (1.00)
Abstract In deepwater and ultra-deepwater wells with multiple zones to complete, single-trip multizone completions are an increasingly common alternative to standard stacked completions. Several trips are saved by avoiding running plugs, stimulating, and then running sections of completion equipment. In addition to running the completion, stimulating, and gravel packing in a single run, today's multizone systems are rated for higher operating pressures, enabling higher pump rates and higher proppant volumes, as compared to conventional stacked completions. Along with the many benefits that single-trip multizone completions provide, they also introduce additional operational challenges in the well-completion process. One of these challenges is that multiple hydraulic set packers and screens must be run through perforation zones prior to being deployed at the intended depth. This necessitates a run to remove flash, burrs, and other debris that are left behind by the perforating operation from the casing and inside of the well. This is commonly referred to as a deburring run. In addition to restoring a smooth casing wall, a sump packer must be cleaned out and sufficient space below the packer cleared of debris for proper installation of the multizone completion. These two critical objectives have been addressed by running an innovative combination of wellbore clean-out tools, toolstring design, and detailed operating parameters.
- Well Completion > Well Integrity > Zonal isolation (1.00)
- Well Completion > Completion Installation and Operations > Perforating (1.00)
Abstract In subsea applications, our Intelligent Casing-Intelligent Formation Telemetry (ICIFT) Systems focus on using fiber optic sensing methods for lifetime monitoring of a well and its reservoir. The production casing and/or formation/cement outside the casing are instrumented with fiber optic cables that require continuity connections with other fiber optic cables that exit the wellhead. Two new technology tools are needed to join two fiber optic cables downhole laterally across an annulus. One is a "lateral" fiber optic (FO) pressure balance oil filled (PBOF) wet-mateable connector. The other tool needed and the one addressed in this articel is one that can align two FO cables with millimeter precision for connection laterally across an annulus. For that purpose, a downhole autonomous robot rendezvous tool is designed that can align two FO cables at a lateral crossover point with millimeter precision; two prototypes are constructed and tested. The setting of this research is to bring fiber optic cables through the wellhead in the annulus outside the production tubing, down through the production packer, and crossing laterally in the annulus over to the production casing. The autonomous robot rendezvous tool developed with prototypes and tested uses two subassembly designs: a tubing subassembly design and a casing subassembly design. The objective of the autonomous robot rendezvous tool is to align the two subassemblies with millimeter accuracy in two dimensions (i.e., in depth direction and in angular rotational direction). The designs of the two subassemblies are developed for popular subsea 7" OD production tubing and 9 5/8" OD production casing and for a completion fluids-based annulus environment (e.g., brine, water, and diesel). Test results of the two prototypes provide 5 mm "ballpark" accuracy for rendezvous alignment in the depth direction and 2 mm accuracy for rendezvous alignment in the angular direction. The development of the autonomous robot rendezvous tool is one step in the direction of making the reservoir intelligent outside the production casing via all means of distributive fiber optic sensing methods without the need for power and electronics downhole during the lifetime of well.
- Well Drilling > Casing and Cementing > Casing design (1.00)
- Well Completion > Completion Installation and Operations (1.00)
- Production and Well Operations > Well & Reservoir Surveillance and Monitoring > Production logging (1.00)
- Information Technology > Communications > Networks (1.00)
- Information Technology > Artificial Intelligence > Robots (1.00)
Abstract The electro-hydraulic firing head features a novel combination of electronic control over a hydraulic firing mechanism. An electronics module senses wellbore pressure and, upon seeing a distinct signal, opens a valve that allows downhole pressure to operate a hydraulic firing mechanism. The hydraulic firing mechanism is extremely reliable, does not have sufficient energy to fire until safely downhole, and is immune to electromagnetic interference. The electronic control system prevents inadvertent pressure applications from prematurely activating the firing head. This combination of electronic control and hydraulic firing in a firing head offers unique and distinct benefits in safety, operational flexibility, and risk reduction. On a recent job, a TCP assembly with dual electro-hydraulic firing heads (stacked vertically for redundancy) was run below a permanent packer and isolation valve. The electro-hydraulic firing head enabled this deployment to be conducted safely, with reduced risk of NPT, and in a single trip. A hydraulic firing head could not be used in this application due to the risk of pressure communication through the isolation valve during packer setting and testing. The TCP assembly was hung off the packer with a ballistically actuated automatic release. The electro-hydraulic firing head has a detonating cord bypass, allowing it to detonate guns below at the same time as actuating the release above. The availability of this firing head allowed this job to be performed more safely, more efficiently, and with reduced risk of NPT than was previously possible. This paper will present an overview of the design and features of the electro-hydraulic firing head, discuss the recent successes in utilizing its unique abilities to enable more efficient job plans, and discuss other unique applications for this technology.
Abstract Large-diameter, long-interval tubing conveyed perforation (TCP) operations are an important part of modern deepwater completion design. Safe and cost-effective designs require an understanding of the interdependence between a large set of static and dynamic parameters that characterize the downhole processes affecting a complex well completion. Typically, it is impractical to measure such parameters in a downhole environment. For this reason, physics-based modeling and numerical simulation of transient processes such as static/dynamic underbalance, perforation cleanup, and shock loading are a critical component of the design process. A significant challenge is that these downhole processes are typically modeled with a dynamically coupled system that includes the reservoir, wellbore, perforation tunnel, tool string and fractures, leading to long simulation times. This is not desirable due to the fact that a single design must satisfy constraints over a large design parameter space, and therefore requires many simulations. This paper introduces a fast computational tool based on dominant flow physics of the perforating process. The new model is benchmarked and verified against current industry-standard dynamic simulators, as well as computational fluid dynamic (CFD) packages. The novelty of this approach is based on physics at the right scale, resulting in a computational efficiency improvement and simulation times at least an order of magnitude less than other industry-standard simulators. Results for numerical examples representing downhole perforating scenarios provide unique insight into underbalance (i.e., using pressure transients), and subsequent cleanup mechanisms. In this study, a new fast computational model of the perforation process has been developed based on dominant physics. The benefits of this novel approach include design parameters that are closely tied to the flow physics, and simulation results that are easily interpreted for enhanced perforating job design. Ultimately, these benefits enable the completion engineer to make more informed and faster decisions during the design of a perforating job.
Abstract Propellants have been used in the oil and gas industry for a wide variety of applications including well cleanup, damaged zone treatment, and stimulation. In particular, propellants have a unique place in the industry as a stimulation / enhancement tool that can significantly improve productivity and lower operator costs. However, the success of a propellant-stimulation job depends not just on the operational design/deployment, but also the pre-job evaluation using predictive modelling tools. This paper focuses on providing insight into the processes involved in propellant-based stimulation, successful case histories (propellants used as standalone tools and combined with the perforating process), and the modeling tools that are used to design and optimize propellant jobs. Case histories showing the benefits of using these tools to lower workover costs and restore productivity for injection and production will be presented. When used as a pre-frac perforating tool, propellants can reduce horsepower requirements by up to 35% in some cases. Along with the propellant tools, a dynamic perforation modeling tool successfully models the event beforehand to mitigate risk and predict the viability of the process. The software simulates the dynamic response of a cased or uncased wellbore, its contents and the porous rock formation, to the energy released by gas-generating and stored pressure sources. In particular, the modeling tool can be applied to predict fracture propagation, near-wellbore cleanup and skin reduction during wireline and TCP operations. The results from the case histories and the insight provided by the dynamic modeling software illustrate that, when properly applied, propellant tools can add tremendous value to completion operations by lowering costs and enhancing production. This paper also provides the framework for a completion engineer to better understand the design and optimization of a propellant-stimulation job.
- Asia (0.93)
- North America > United States > Texas (0.48)
- Well Completion > Hydraulic Fracturing (1.00)
- Well Completion > Completion Installation and Operations > Perforating (1.00)
- Production and Well Operations > Well Intervention (1.00)
- Data Science & Engineering Analytics > Information Management and Systems (1.00)
Abstract As the Oil and Gas industry looks forward to perforating next-generation complex wells (including but not limited to HPHT, deepwater, geothermal, multi-stage long horizontals etc.), computational modeling tools have been increasingly used to predict the transient flow physics that govern the design and optimization of perforating jobs. In particular, it is crucial to accurately predict the unsteady wellbore flow dynamics and relevant shock physics that typically occur during perforation jobs. Such modeling capabilities provide us the ability to prevent downhole equipment failures that may result from shock loading as well as lead to accurate predictions of perforation cleanup process which depends on balance of pressures in the reservoir, wellbore and gun. In addition, as complex completions such as those found in subsea wells and long horizontal wells are becoming more important, so is the need to extend such a predictive capability to higher-pressure and higher-temperature environment that often accompanies such wells. To address the above, this study is focused on the development and verification of a next-generation transient wellbore flow simulator that is used in conjunction with our existing perforation modeling software. The use of appropriate numerical algorithms allows the simulator to accurately capture unsteady compressible wellbore flows with large gradients of flow quantities. The set of governing equations for compressible flows are closed with improved thermodynamic equations of state, specifically designed to model extreme high pressure (up to 40,000 psi) and temperatures (up to 600 °F). Computational results from various shock-tube test cases show good agreement among exact solutions, single-phase numerical solutions, and the new three-phase solutions. Compared with our existing perforation modeling software, the next-generation simulator exhibits improved accuracy for HPHT environment, better shock-capturing properties, and improved computational efficiency. This unique computational tool has been integrated into an existing perforation job-design workflow to realize significant improvements in risk mitigation and design parameter optimization. This improved workflow enables a new decision process to better model and design challenging deepwater/HPHT perforating applications.
- Well Completion > Completion Installation and Operations > Perforating (1.00)
- Reservoir Description and Dynamics (1.00)