Electrical submersible pumps focuses on the standard ESP configuration. It has the pump, seal chamber section, and motor attached to the production tubing, in this order from top down. In some wellbore completions and unique ESP applications, the arrangement and configuration of the system is modified. For a bottom-intake design, the production fluid is drawn in the intake ports located at the very bottom of the ESP system and discharged out of ports located just below the connection to the seal-chamber section. Because the discharged production fluid cannot flow through the seal-chamber section and motor, it has to exit into the casing or liner annulus and flow past these units.
The packer (more accurately described as the'upper completion production packer') is a key piece of downhole equipment in many completions - a sealing device that isolates and contains produced fluids and pressures within the tubing string; it is a well barrier element, usually part of the well's primary well barrier, protecting the casing and creating an A-annulus. The packer is essential to the basic functioning of most wells, injectors or producers. Alternatives to using a production packer include a dynamic seal assembly, a cemented completion and a packerless completion. The slip is a wedge-shaped device with wickers (or teeth) on its face, which penetrate and grip the casing wall when the packer is set. The cone is beveled to match the back of the slip and forms a ramp that drives the slip outward and into the casing wall when setting force is applied to the packer. Once the slips have anchored into the casing wall, additional applied setting force energizes the packing-element system and creates a seal between the packer body and the inside diameter of the casing. Permanent packers can be removed from the wellbore only by milling. The retrievable packer may or may not be resettable, but removal from the wellbore normally does not require milling. Retrieval is usually accomplished by some form of tubing manipulation.
Installation of such components on all wells may not be justified, but their use on key wells should be carefully considered. Because the ESP operates in a hostile and confined environment, monitoring how it operates is very difficult. Additionally, it is also difficult to find sensors and electronics that operate reliably and long term under the range of downhole conditions required. The ESP's reliability or run-life is directly related to the continual monitoring of its operating parameters and the wellbore conditions. Not only is this information critical to the run-life, but it is also important for the evaluation of the application design of the ESP system in the hole. This evaluation can provide guidance on possible operational changes that can be made to optimize the current system or the ESP design changes needed to optimize the application.
Kollamgunta, Saikiran (National Petroleum Construction Company) | G. V. R. A., Srinivasa Rao (National Petroleum Construction Company) | Singh, Harendra (National Petroleum Construction Company) | Kamal, Faris Ragheb (National Petroleum Construction Company) | Takieddine, Oussama (National Petroleum Construction Company)
One of the major challenges in the upstream oil and gas industry is de-bottlenecking of existing slug catcher/ inlet separator system during facilities up-gradation or due to changes in production rates for any other reasons. It is often found that upgrades or changes result in increased slug volume from the upstream pipelines thus making existing slug catcher or separators inadequate to handle the increased load. Even in cases of normal pigging not involving debottlenecking of existing facilities, production rates are required to be lowered. This is done as excess liquid slugs generated due to pigging may show severe operational problems in terms of level and pressure fluctuations in a separator leading to poor separation, potential liquid flooding, increased flaring, emergency shutdown and production loss. The use of by-pass pigs can effectively reduce the liquid arrival rate at the slug catcher over conventional approach by delivering a more uniformly mixed fluid even at relatively higher production rates. It thereby reduces the slug volume and hence, the requirement of increased surge capacity. Further, in brownfield applications, it enables optimal use of existing assets or avoiding new slug catcher.
Operators are reluctant to reduce the production flow rate to very low value for pigging, as this normally results in reduction in revenue. Bypass pigging, as compared with conventional pigging, is able to reduce the pig velocity even at relatively higher production rates. It, however, requires careful evaluation and design as in many cases, such as well fluid having wax, solids or high asphaltenes may result in blockage of the bypass holes thus impacting the effectiveness of the operation. Transient modeling and simulation of bypass pigging using OLGA Dynamic Multiphase Flow Simulator has been performed to address such issues.
This paper describes the strategies to address de-bottlenecking challenges due to increased surge volumes to be accommodated in the existing slug catcher/ separator system and use of by-pass pigging to overcome these. The application of the technique used i.e. bypass pigging is demonstrated by transient multiphase simulation using OLGA dynamic simulator. Proposed design solutions are based on NPCC's extensive and successful experience in tackling challenging Brownfield projects.
Traditional well plugging and abandonment (P&A) methods are not efficient. For example, section milling is time-consuming and expensive because of the number of rig days required. The milling produces cuttings, which have to be handled. Contamination of the milling fluid with oil-based mud (OBM) requires separation before disposal. Cutting casing requires pulling it from the hole.
Artificial lift utilizing Electrical Submersible Pump (ESP) supporting operations have evolved from pump installations with no access to the completion zone to the point where rigless logging intervention operations can access the lower wellbore using either coiled tubing or wireline. Access to the completion zone has been accomplished through the installation of Y-Tool and a by-pass leg in conjunction with the ESP.
The major challenge is to have the Coil Tubing (CT) plug seal assembly located on the coil otherwise a damage to the seal assembly is expected and consequently a fluid circulation might take place. CT conveyed production logging requires a CT plug to prevent production circulation across by-pass section while operating the ESP. The circulation is prevented by the seal assembly which exists in the CT plug and located on the coil tube. The Bottom Hole Assembly (BHA) consist of CT plug which included connector, sleeve and bottom crossover, all covered by the CT plug external body which has the seal assembly in addition to the Production Logging Tool (PLT). Changes in tools design and profiles allowed for a successful logging intervention into these Y-tool equipped wells while gathering required well logging data.
The paper presents technical and logistic challenges during rig-less logging operations on wells with a Y-tool and a by-pass leg with complicated downhole configuration including small restriction and dual pump layouts. Examples of both impaired and successful operations will be reviewed with challenges and lessons learned, including the changes made to allow the tools for logging activities. This paper will provide a path forward to well access and surveillance while ensuring adequate isolation during logging operation.
The reliance on Electrical Submersible Pumps (ESPs) in oil fields operations is increasing and will continue to grow in the coming years due to the eminent decline of reservoir pressure and early water breakthrough associated with high production demand overtime. More ESPs will be required to sustain production for a period of time. In addition, more wells’ data acquisition and interventions will be frequently required to monitor wells integrity and performance. Therefore, an ESP system with Y-tool bypass section is utilized to enable data gathering and access to the wellbore below the ESP assembly using coil tubing (CT) or wireline (WL) deployed interventions. Production logging operations are required to monitor well performance, water production intervals, and other well parameters via the Y-Tool-ESP completion.
The Field M phase 1 development consists of 9 production wells and 2 water injectors in offshore Sabah. Field M is the first Tension Leg Platform (TLP) in Malaysia with several unique flow assurance features that were challenging for the project, namely hydrates, waxy crude with high pour point and cloud point temperatures, bypass pigging for wax as base-case strategy as well as an industry first Single Combo Top Tension Riser (SCTTR) with both gas lift and production strings in a nitrogen filled riser annulus. This paper describes the experience of bringing the Field M field into operation including hydrate inhibition, well unloading, dewatering, well ramp-up and ongoing steady state operation from a flow assurance perspective. The initial well unloading process and ongoing steady state operation of the wells and flowlines are described, and comparisons are made between expected responses based on steady state and transient simulations during the design phase, and actual field data. The key challenges faced and technical findings are also documented. Lessons learned during the first year of operation are a combination of work-arounds, differences in fluid properties from those initially assumed, benchmarking of field data with predicted simulation results, and general operational experiences related to flow assurance.
The objective of this paper is to share lessons on stabilizer selection with the industry that minimize drilling and tripping problems. Ideally the stabilizers and BHA will drill a round, ledge free hole, without patterns, with minimum vibration, minimum unplanned dog legs, that reach all directional targets in one run per section. They should not constrain ROP, be able to trip in and out on elevators past ledges and hole irregularities without the need for rotation.
These lessons were based on a number of forensics observations while drilling and tripping and a physical understanding of the BHA and its effects on vibrations, trajectory, and tripping in high angle holes.
A draft of these lessons were presented at a SPE Gulf Coast section meeting in 2015 and were sent to all that requested them as well as suppliers used by this operator for comments and suggestions. It is hoped that this publication and the reasoning behind the lessons will help improve this often neglected tool.
A few significant events initiated this work. The first was a mechanical sticking event in 17 ½ inch hole where the BHA could be rotated and moved downward, but hung up trying to trip out. The formation being drilled at high angle was a vuggy limestone. Inspection of the BHA and stabilizer design found that there was a sharp, 75 degree, transition taper on one of the rotary steerable system stabilizers. This coupled with a formation ledge made it impossible to ream or trip, resulting in a lost BHA and sidetrack.
The second key event was a 6 ¾ BHA that required control drilling to avoid plugging the near bit stabilizer. This showed up as an increase in standpipe pressure and a decrease in an annular pressure gauge located above this stabilizer. The root cause was low bypass area on the near bit stabilizer.
The third event was in 12 ¼ inch high angle hole in soft rock. This required circulation on the trip out of the hole on some wells and not others. The wells requiring circulation on the trip out had high spiral stabilizers that packed off rather than passing the cuttings bed.
A practical set of lessons have been developed that may be used as a starting point for developing industry best practices. The physics behind these lessons are given so that they can be improved over time. One improvement expected is the requirement for low coefficient of friction on the stabilizer OD to minimize whirl and on the end tapers to reduce tripping hang up.
Traditional sand-management programs usually consist of several measures employed to mitigate the production of sand from wells, a process commonly referred to as sanding. Such systems include production prediction and monitoring, topside management, sand control, and "intelligent" systems (Gherryo et al. 2009). Sand control can be considered in terms of short-and long-term solutions; examples of long-term solutions (preventative measures) would be the application of gravel packs, screens, inflow control devices, and chemical stabilization methods (Abney et al. 2007). In instances where a sand-management program has not been employed or has been ineffectively delivered, sand can and is deposited in pipelines/riser systems. This can be a gradual process of continual minor deposition over time, or systems can be overwhelmed with a sudden influx of sand as a consequence of formation or completion failure. The result leads to increasing pipeline resistance, reduced flow rates, rising pressure drop in the pipeline system, and erosion, which, in turn, can lead to degradation of the pipeline/riser and topside systems (Abney et al. 2007).
Bypass pigging, compared with conventional pigging, reduces the damaging effects of the pig-generated liquid slug by redistributing gas and liquid in the pipeline. Oil-and gas-production rate, high liquid-slug flow to the slug catcher, high pipeline backpressure, and the capacity of the slug-handling facility at the receiving end are major considerations when designing a bypass-pigging solution. Various operational and engineering challenges are encountered while implementing the commonly known bypass-pigging solutions, and empirical correlations are developed on the basis of experimental results and compared with simulation results. This paper suggests an innovative bypass-pig geometry as a solution. The Thornhill-Craver equation is introduced to calculate the bypass-flow quantity and the pig velocity.