When producing hydrocarbons from an oil well, managing erosion of both surface and subsurface components caused by solids in the flow stream is critical to maintaining operations integrity in both land and offshore assets. Although component lifetime prediction has advanced in the past few decades, the prediction's accuracy remains a major oil and gas industry challenge. Current computational models only provide an initial erosion rate which is usually assumed constant until equipment failure. However, observed erosional rates vary as a function of time due to the geometrical changes caused by equipment material loss, which result in variations in solid particle impingement velocity [
This paper presents an implementation of an erosion dynamics model in ANSYS FLUENT, a commercial computational fluid dynamics (CFD) software, to capture the progression of transient erosion. The model has the capability to capture the effects of surfaces receding from erosion at each time interval. By dynamically adjusting these surfaces and recalculating the local flow conditions in the area, this method can predict new erosion rates for each time interval and achieve fully coupled geometry-flow-erosion interactions.
This new erosion dynamics model was validated against experimental data from both literature and physical testing, and was determined to have accurately captured the observed erosion trends over time in terms of location and magnitude. The model was then employed to study two real world applications: 1) in evaluating the erosion risk for a high-rate water injector, it predicted the evolution of damage to a coupler designed to connect different diameter pipes, and 2) in analyzing facility piping systems connected to an unconventional well, it predicted the transient erosion trend from proppant flowback, which allowed for pipe geometry optimization to increase in erosional life expectancy.
Morrow, Timothy (ADNOC-Offshore) | Al-Daghar, Tariq (ADNOC-Offshore) | Troshko, Andrey (ExxonMobil Upstream Research Company) | Schell, Caroline (University of Tulsa) | Keller, Michael (University of Tulsa) | Shirazi, Siamack (University of Tulsa) | Roberts, Kenneth (University of Tulsa)
The long-term development plan for a giant oil field offshore Abu Dhabi calls for new extended reach wells drilled from artificial islands. The existing wells in this field have historically suffered from inorganic sulfate-based scale deposition in the production tubing which is mitigated by periodic scale inhibition squeeze treatments. The new extended reach wells will have more sophisticated lower completions, including limited-entry liners (LELs) and inflow control devices (ICDs) with external debris barriers. It is currently planned to mitigate inorganic scale in these wells with periodic coiled tubing or bullhead scale inhibition squeeze treatments, which are anticipated to be more challenging and costly due to the extended reach. It is unknown as to whether these types of completion equipment are susceptible to scale deposition or how much scale deposition can be tolerated before well productivity is impacted. Knowledge of the rate of scale buildup on ICDs and LELs versus the volume of water produced through the devices is an important factor for choosing the optimum frequency for scale inhibition squeeze treatments to mitigate scale in these completions while keeping operational costs down. A two-phase laboratory study is currently underway to assess the susceptibility of ICDs to scale deposition. The first phase of the study will focus on the potential for strontium sulfate scale deposition on the debris barrier upstream of the ICD. This paper reports the experimental design and results of laboratory scale deposition experiments on a series of debris barrier test coupons with the goal of estimating the rate of scale buildup on the full-size ICD debris barriers, and the volume of scaling brine that can be produced through the ICD debris barrier (in the absence of any scale inhibitor chemical) without risking significant plugging.
A new generation of sophisticated wells are to be drilled in a giant offshore field in Abu Dhabi. These extended reach wells will reach and produce remote areas of the field from artificially built islands. The first maximum reservoir contact (MRC) pilot well was drilled successfully with 20,000 ft total depth and a 10,000 ft producing interval completed with inflow control devices (ICDs). The well started producing dry oil at reasonably high flow rate and uniform contribution from each ICD compartment. After a relatively short period of dry oil production water break-through occurred and started causing unexpected downhole flow assurance concerns, especially at the locations of the ICDs. Production logging along with caliper data showed severe corrosion around water producing ICD nozzles and high gamma ray readings in the water producing intervals, suggesting that scale had precipitated behind pipe either in the near wellbore rock (believed to be unlikely based on the history of scale precipitation in the field) or on the outside of the completion (thought to be more likely).
An investigation was launched to determine the cause of the corrosion around the ICD nozzles and improve understanding of the influence of ICD flow dynamics on scale deposition and material corrosion, with the objective of developing a suitable mitigation method for scale and corrosion in future MRC/ICD wells. The study results showed that high wall shear stress developed in and around the water producing ICD nozzle area are at the origin of the corrosion in the pilot well, and that low-to-moderate wall shear stresses on and around the wire-wrapped screen sections of the ICDs could be the cause of the scale deposition. Consequently, the completion design for future wells with ICD completions has been revised to mitigate the risks of flow induced corrosion.
This paper will present results of the laboratory study into the influence of ICD flow dynamics on corrosion rates and mineral scale precipitation and discuss strategies for mitigating both concerns via the design of the ICD.
Edmonstone, Graham (Zakum Development Company (ZADCO)) | Jackson, Alfred (Zakum Development Company (ZADCO)) | Kofoed, Curtis (Zakum Development Company (ZADCO)) | Shuchart, Chris (ExxonMobil Upstream Research Company (URC)) | Troshko, Andrey (ExxonMobil Upstream Research Company (URC))
The recent industry development of drilling ERD wells with horizontal laterals in the reservoir of 10,000 ft. or more has led to a greater use of passive flow control devices and swell packers to achieve the desired inflow or outflow profiles. Another desire is to perform stimulation treatments of the lateral especially in tight carbonate formations. However, such treatments can create high velocities through the Inflow Control Devices (ICDs) that inevitably leads to high turbulence and wall shear stress in the ICD which can cause severe erosion and corrosion of commonly used materials. There appears to be little experience and associated knowledge on corrosion mitigation to ensure ICD integrity after well stimulation.
Alvarez, Adriana Carolina (ZADCO) | Samad, Saleh Abdul (ZADCO) | Jackson, Alfred M (ZADCO) | Bachar, Sofiane (ZADCO) | Kofoed, Curtis Willard (ZADCO) | Edmonstone, Graham (ZADCO) | Abdouche, Ghassan (ZADCO) | Shuchart, Chris E. (ExxonMobil Upstream Research Co.) | Troshko, Andrey (Exxon Mobil Corporation) | Mayer, Christian (ExxonMobil)
For the last 30 years, wells in the field have been suffering from medium to high corrosion rates in both near surface and downhole components. Remedial measures had been implemented in order to restore Well Integrity with different techniques. Corrective actions aside, a strong preventive approach is needed to better understand the root causes of such corrosion rates and scenarios where the integrity of specific wells has been seriously compromised due to corrosion problems. Taking a step further and considering the big implications of new projects such as Artificial Islands project, where the company will be drilling & completing over 300 Extended Reach Drilling (ERD) wells, Well Integrity input as a discipline becomes critical in order to ensure previous problems will not be repeated and all lessons learned throughout the years will be wisely taken into consideration when designing a new well to remain integral during its whole expected life. Understanding of the current corrosion mechanisms in the field was the key to find not only solutions, but also, to create an approach aimed to improve the future completion for Island wells in terms of design, materials and many other factors. An extensive multidisciplinary approach was carried out in order to successfully complete a full study in one of the pilot wells completed with Inflow Control Devices (ICDs), which will be analyzed in detail in this paper, covering the following areas: i. Well design and configuration ii.
Edmonstone, Graham (ZADCO) | Kofoed, Curtis Willard (Zakum Development Co.) | Jackson, Alfred M (Zakum Development Co.) | Parihar, Shardul (ZADCO) | Alvarez, Adriana (ZADCO) | Mumtaz, Saad (ZADCO) | Abdouche, Ghassan (ZADCO) | Shuchart, Chris E. (ExxonMobil Upstream Research Co.) | Mayer, Christian Sebastian Jakob (ExxonMobil Upstream Research Co.) | Troshko, Andrey (Exxon Mobil Corporation)
As part of the Islands Project which involves the use of 4 artificial islands to drill & complete over 300 ERD wells in a giant offshore oilfield, several completion designs have been piloted to test & monitor their suitability for the brownfield development. One well design incorporated the use of Inflow Control Devices (ICDs) & swell packers which was ZADCO's first use of such technology in a production well. The technology was installed in the pilot well to test inflow control along a 10,000ft lateral & to manage future water production. The Paper will cover: i. The design of the well detailing the ICD configurations & swell packer arrangements providing 15 compartments along the reservoir section, ii. The inflow performance recorded annually along the lateral showing differing results, iii. The outcome of an extensive intervention program in 2013 utilising different logging tools to record internal & external data, live camera to view condition in low water cut well & venturi tool to recover downhole samples that concluded the mechanical failure of ICDs in the heel, iv. The extensive post-failure investigation undertaken such as extensive review of installed ICD design, flow assurance, computational fluid dynamic (CFD) simulations, laboratory testing for different conditions & materials, comparison of modelled with actual data to determine failure mode & v. The way forward for future ICD installations with initial short term solution & plans for future long term design solutions to give a required 30 year life.
Effective acid stimulation can be critical to achieving the desired long-term production rates from targeted reservoir layers. ExxonMobil has developed an integrated, multi-disciplinary methodology for carbonate matrix stimulation of long completion intervals.1 The methodology is a continuous process which includes geological characterization, reservoir objectives, completion strategy, stimulation design with the necessary experimental testing, implementation, and evaluation. The methodology has recently been customized in collaboration with RasGas to achieve objectives for K1-K32 and K1-K43 completions in the North Field, the world's largest, non-associated gas field.
Building upon this success, ExxonMobil continues to study the fundamentals of carbonate stimulation and its impact on long-term productivity to enhance the process and apply it to a wider range of reservoirs and well types. This paper presents preliminary results from three areas of ongoing research: (a) improved understanding of 3-D wormhole growth through large-scale experiments and visualization techniques, (b) integrated wormhole modeling and complex fluid flow during stimulation of long horizontal wells, and (c) enhanced post-stimulation evaluation method that integrates stimulation physics, well test analyses, and long-term reservoir performance predictions. Integration of these technological advancements with existing knowledge provides an enhanced methodology for the stimulation of carbonate reservoirs with an increased focus on long-term productivity.
Yeh, Charles S. (ExxonMobil Upstream Research Co.) | Moffett, Tracy (ExxonMobil) | Petrie, Dennis H. (ExxonMobil Upstream Research Co.) | Entchev, Pavlin B. (ExxonMobil Upstream Research Co.) | Long, Ted (ExxonMobil Upstream Research Company) | Troshko, Andrey (ExxonMobil Upstream Research Co.) | Grubert, Marcel Andre (ExxonMobil Upstream Research Co.) | Dale, Bruce A. (ExxonMobil Development Co.) | Barry, Michael D. (ExxonMobil Development Co.) | Hecker, Michael Thomas (ExxonMobil) | Howell, David A.
MazeFlo™ technology enables a sand control screen to self-mitigate mechanical damage and improve reliability in sand-prone well production. A self-mitigating screen uses redundant sand control screens and compartment baffles to restrict the effects of any mechanical screen failure to a local compartment. The hydrocarbon flow continues intact through the remaining undamaged screen compartments. This innovative, patented technology is being commercialized in collaboration with a selected service company.
This paper reviews the initial design and development of the self-mitigating screen prototype. The screen design balances flow hydraulics, well performance, mechanical integrity, and manufacturing complexity all while maintaining practical screen dimensions. Successful self-mitigation, after failure of an outer screen, requires that the incoming sand packs a compartment to shut off the flow path before any significant erosion occurs along the flow path to the redundant inner screen. The baffles are configured to both redirect fluid momentum from any "hot spot" inflow at the outer screen and impose a minimal friction loss during production through undamaged compartments. Each component in a compartment is designed to sustain erosion from the incoming sand of a failed outer screen. The offset outer and redundant inner screens are sized to minimize the impact on productivity when compared to conventional screens. The mechanical strength of the self-mitigating sand screen is also targeted to be equivalent to conventional screens.
Development of the self-mitigating screen prototype is proceeding and includes extensive qualification by multiple modeling techniques and physical testing. The innovative, self-mitigating capability expands the current operating limits of screens in sand control completions. In a broader view, the self-mitigating screen enhances overall reliability and longevity and can be integrated with other emerging technologies such as openhole zonal isolation, inflow control, and intelligent wells for enhanced production flexibility. MazeFlo sand screens will expand ExxonMobil's suite of innovative sand control solutions that include Alternate Path® technology, NAFPacSM process, openhole gravel packing with zonal isolation, and customizable sand control for extreme length completions and injection conformance.