Housingless ESPs for Slim Completion Wells

This paper describes a new electrical submersible pump (ESP) design concept to overcome the challenges of applications in slim well completions or thru-tubing deployment. The housing of the conventional pump is removed, allowing the pump impellers to have a larger diameter. The impact of this design change on pump hydraulic performance is assessed in this paper. Downhole ESPs operate in environments where space is limited radially. This is especially the case for slim completions or for thru-tubing rigless deployment. To provide the required rate and total dynamic head, the current approach is to use permanent magnetic motors and operate the slim systems at rotational speed over the conventional speed of 3500-4000 RPM. High-speed operations require new pump stage designs to minimize erosion and vibration. This paper provides an alternative pump design, which removes the pump housing with the benefit of increasing the impeller tip diameter, and hence potentially reducing pump length and operational speed. To ensure the pump retains the well fluids, the diffusers are designed to be externally threaded with an O-ring feature. The centrifugal pump affinity laws are applied to evaluate the impact of removing the pump housing and increasing the impeller outside diameter. A typical ESP housing wall thickness is about 0.18-0.25 inch. With the housing removed, the incremental space available for the impeller tip to occupy is increased by 0.36-0.5 inch. Analysis shows that, for the same pump speed as a conventional pump with a housing, a housingless pump will increase the head generated by 23-32%, and the rate capacity about 36-51%, depending on the pump series. In general, the smaller the pump outer diameter, the greater the flow and head capacity increase. This is because the available space due to removing the housing becomes a considerable size of the impeller tip diameter for the smaller series pumps. The elimination of pump housing enables impellers with a larger diameter to be used to generate more head per stage. In comparison to a conventional pump of the same outside diameter, and providing the same amount of total dynamic head, the housingless pump can have fewer stages and a shorter length or operate at a reduced speed. The reduced length can help mitigating pump-bending stress for installation in deviated or horizontal wells. The reduction in required operating speeds will reduce pump wears, heat generation and vibration. The housingless ESPs have applications for slim well completions or thru-tubing deployments.

Coiled Tubing Workflow Leads to Successful Completion of Multistage Fracturing in Extended-Reach Wells of Aishwarya Field, Barmer, India

Coiled tubing (CT) was used to perform multistage fracturing treatments from the CT-tubing annulus in extended-reach wells of Aishwarya Field, Barmer, India. The wells were completed with chrome completion and included multiple fracturing sleeves. With peculiar challenges faced, solutions and lessons learnt are herein captured. In particular, casing deformation was observed in transverse wells, for which the workflow was developed so the wells with post-fracturing casing deformation could be completed and delivered for production. During the initial phase of the campaign. CT got stuck eight times after fracturing due to casing deformation. In three instances, the bottomhole assembly was left in the hole, and twice the CT was cut for recovery. After the workflow was implemented, no CT stuck incidents occurred due to casing deformation, and all 16 transverse wells in the campaign were delivered successfully. This study highlights the importance of differentiating between transverse and longitudinal wells while understanding their implications. In wells where casing deformation can occur, the workflow for CT-assisted multistage fracturing (MSF) operations must be adjusted. A smaller outside diameter (OD) shifting tool needs to be used without a packer assembly, and the CT cannot stay in the well during fracturing.

Assessment of in situ properties of municipal solid waste with a large-diameter borehole method

A Municipal Solid Waste Borehole Assessment (MBA) was developed to assess in situ geotechnical properties of municipal solid waste (MSW) during the boring of gas extraction well construction. A Large-Diameter Borehole Caliper (LDBC) was lowered into the borehole to measure the diameter and record the condition of the wall by time-lapse video photography. The results indicated that the borehole experienced significant radial compression with depth following completion. Radial compressions amounted to approximately 7.5% at 9.14 m, 10% at 21.3 m and 11% at 27.4 m below ground surface. The bulk modulus was estimated by using the captured volumetric strains and reported lateral earth coefficients, and the results showed that it increases with increasing depth. For MSW, the bulk modulus increased up to 13.4 MPa in a linear trend with depth. The unit weights of MSW were obtained using three diameter readings from LDBC, auger barrel outside diameter and outer cutting bit outside diameter. The results showed that the diameter based on outer cutting bit yielded realistic unit weights (5.08–9.68 kN m–3) due to unrealistic calculated saturations by other two assumed diameters. The borehole assessment with LDBC was shown to be an efficient and valuable means for characterising MSW and effectively designing gas extraction wells. The research provided a means to assess the waste mass with accuracy at great depths by directly observing and measuring borehole condition.

Overcoming Challenges of Mechanical Lifting Capabilities on Offshore Installation by Utilizing Coiled Tubing Boat Spooling Technique

Coiled tubing (CT) operations in the Norwegian continental shelf (NCS) often require a long and large-outside-diameter pipe due to big diameter completions, deep wells, and the need for high annular velocity during fluid circulation. However, getting the CT string onboard becomes a challenge when the crane lifting limit is 35 t, and using a standalone crane barge increases the cost of the operation. The alternative is spooling the CT from a vessel to the platform. Boat spooling is done by placing the CT string on a floating vessel with dynamic positioning while the standard CT injector head is secured at the edge of the platform to pull the pipe from the vessel to an empty CT reel on the platform. The boat is equipped with a CT guide; special tension clamps; and an emergency disconnect system, which consists of a standard CT shear-seal blowout preventer. The technique requires careful study of the platform structure for placement of the injector head support frame, metocean data of the field, and equipment placement on the vessel and platform. The boat spooling operation of a 7,700-m long, 58.7-t, 2.375-in.-outside-diameter CT string was successfully executed for a platform at 70-m height from mean sea level. The total operating time from hooking up the vessel to successfully spooling the string only took 12 hours. Historically for the region, the method has been attempted in sea state of up to 4-m wave height and 16 knots maximum wind speed. For this operation, the spooling was carried out during an average sea state of 2-m wave height and 15-knot wind speed. The continuous CT string allows a telemetry cable to be installed inside the pipe after the CT is spooled onto the platform reel, enabling real-time downhole measurements during the intervention. Such installation is not possible or presents high risk if the CT string is taken onboard by splicing two sections of pipe together with a spoolable connector or butt welding. From a cost perspective, the boat-spooling operation had up to 80% direct cost saving for the operator when compared to other methods of lifting a single CT string onboard, such as using a motion-compensated barge crane. The planning for the boat spooling included several essential contingency plans. Performing a CT boat spooling operation in a complex environment is possible and opens new opportunities to use longer and heavier CT strings, with lower mobilization costs. Such strings enable more advanced and efficient interventions, with the option of using real-time CT downhole measurements during the execution of a wide range of production startup work. This, in turn, is critical to support the drilling of more extended reach wells, which allow access to untapped reservoirs.

THE INFLUENCE OF STIRRER ON THE DRYING OF WHEAT PARTICLES IN A FLUIDIZED BED AT LOW AIR VELOCITY

This study represents an attempt to reduce the drying time of wet grain wheat of the fluidized bed dryer (FBD), using straight blades, and debates the effect of stirrer on the whole drying time at different static bed heights. Experiments for FBD were conducted at the low velocity of air supply (1.45 cm/s) with moisture content for grain wheat 12% and ambient temperature of 37°C for each static bed height (9, 12, and 15 cm). FBD was made from a glass cylindrical column with inside diameter 4.6 cm, outside diameter (5.2 cm) and length (116 cm). The results showed an enhancement of (12- 20.5%) in the total drying time for bed height (9 and 15) cm, respectively. Also, increasing bed height from 9 cm to 15 cm possesses no influence on the equilibrium content of moisture in both techniques of drying either stirred fluidized bed or conventional fluidized bed.

Bearing Design and Lubrication

High rotational speeds of the impeller call for careful bearing design and layout, not just those on the supercharger impeller shaft itself but also on any preceding shafts, which may run at lower speed. The question of whether to use plain (journal) bearings or rolling element bearings can only be decided after a complete evaluation of the overall design of the supercharger drive system in question. Journal bearings are in general smaller in outside diameter and despite the higher overall length have a lower weight than rolling element bearings. Journal bearings demand several times the lubricating oil flow rate than rolling element bearings, and they also exhibit high sensitivity to particulates in the oil and the overall quality thereof.

Industry's First Sidetrack in 12-1/4-in Casing Enables Operator to Re-Establish Production in GOM

In a Gulf of Mexico (GOM) ultradeepwater well, liner integrity issues forced an operator to consider milling a conventional casing exit to sidetrack as deep as possible to re-establish production. Milling a window in 12 -1/4-in. heavy wall casing above the liner hanger had never been achieved before because of the thickness and grade of casing. A successful installation would require significant preplanning and testing to prove capability before real-world application. The service provider recommended an off-the-shelf solution to accommodate a 12 -1/4-in. casing exit. It was determined that the best fit for the application would be the standard equipment used for exits out of 10 -3/4-in. casing, given the similar internal diameters (IDs). Despite never having performed an installation in this casing size, the provider had a successful run history for exits in heavy weight casing strings. Job challenges included avoiding cutting a casing connection, managing swarf, milling through a centralizer, and achieving a low dogleg for production packers. Additional challenges included torque limitations, mill gauge, and the limestone formation. An 8-in. outside diameter (OD) system with mechanical anchor and 9 -7/8-in. OD mills was sent to a test well designed to replicate the target section of the offshore well. Based on determinations made in the planning phase, milling of the window and rathole would be staged in two trips. Additionally, a replica drilling bottom hole assembly (BHA), 8 -5/8-in. casing, and a replica production packer would need to pass through the window to ensure both window quality and low enough dogleg. Dogleg data was acquired through multiple logging runs during the 10-day operation. The installation went as planned, along with an additional custom window elongation run to decrease the dogleg severity to approximately 4.5°/100 -ft (30m). Having successfully validated the equipment for the application, the operator and servicer prover were comfortable moving onto the GOM well. Considering the test results, the team planned to mill the window and rathole in one trip. They achieved the 22 -ft long window and 15 -ft rathole in one run that lasted 26 hours. This installation is the first sidetrack conducted with a whipstock in 12 -1/4-in. casing. This paper shows that a safe, reliable casing exit installation is possible in difficult applications, such as uniquely heavy wall casing, even though it may previously have been considered impossible. This successful application provides the industry with contingency options in similar scenarios.

Fit for Purpose Connection Design for Drilling Operations in Size Constrained Tubular

Drilling out or working within small sizes of casing and liners requires the use of a drill string with small outside diameter tool joints to fit inside the casing/liner bore and, at the same time, a large enough connection internal diameter to pump actuating balls inside the drill string when needed. These requirements significantly limit the available options that can be used. Historically, a drill pipe double shoulder connection with a 3⅛-in. outside diameter (OD) has been used for such operations, as it allows for multiple makeups and breakouts before it needs to be repaired. This is a great improvement compared to using small tubing premium connections that are somewhat limited on the number of makeups. However, the geometry constraints are such that the thin material envelope leads to torsional weakness in the connection, resulting in a higher than expected recut rate as connections can be overtorqued downhole in operation. A research and development (R&D) project was commissioned to improve the connection performance significantly to mitigate the downhole overtorque. Exploring the acceptable connection envelope limits allowed for a slightly reduced internal diameter (ID) when compared to the previously used connection. The team considered different thread designs and decided to use the one that would provide the highest torque. The design process was then followed to develop and qualify a well-balanced connection. The design validation was performed at an engineering technology center in Houston, Texas, where samples were destructively tested to compare the actual capacity of the new connection against the calculated values. It was confirmed that the torsional strength of the new design meets and exceeds the theoretical value, an improvement of at least 85% over the previously used connection, and a first string was built. It was subsequently deployed in the field and the recut rate was monitored to establish that the objective of delivering a connection capable of higher torque was indeed met to resist the downhole overtorque.