bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Coiled Tubing Drilling Rig for Mineral Exploration
Authors: Soe S. , Lagat C. , Evans B. , Mostofi M. , Fox S. 
Published: March 2018

Abstract
In November 2016 the Deep Exploration Technologies Cooperative Research Centre (DET CRC) launched the RoXplorer®, a coiled tubing (CT) drilling rig for greenfields mineral exploration, delivering a platform for low-cost, rapid, safe and environmentally-friendly drilling. The launch represented an important technical milestone in the development of CT drilling for mineral exploration and has been complemented by a series of very successful field trials in the first half of 2017
The paper presents CT technology and its application for mineral exploration drilling. The three key challenges for CT drilling in mineral exploration are coil durability, drilling hard rocks with low weight-on-bit and sample fidelity. Results for mineral exploration CT-drilling field-trials in the consolidated cover rocks of South Australia and the unconsolidated cover rocks of the Murray Basin in Victoria are presented and outline how each of these challenges was overcome. The outcomes confirm the promise of this cheaper regional prospecting approach to mineral exploration drilling. The results of assay samples of the CT drilling cuttings are remarkable; the assay samples from the CT drilling at Port Augusta trial matched those of diamond drill core from an adjacent hole.
Methods and Processes to Help Improve the Operational Efficiency and Reliability of Wireline-Run Cement Plugs
Authors: Wu Q. , Chamarthy P. , Lindsey A. , Thompson J. G. 
Published: March 2018

Abstract
Cement plugs are a widely used well intervention method to achieve zonal isolation and well plug and abandonment. The current practice of cementing using wireline was reviewed on a system level to identify the primary challenges. Existing cement mix properties, such as compressive strength and wait-on-cement (WOC) time, were characterized using standard API RP 10B-2 (2013) tests. The sensitivity of these mixes to various wellbore temperature and pressure conditions was also studied. Based on the understanding of the current practice, modifications of the compositions, packaging, and mixing procedures in the field were proposed and tested accordingly. Based on the experimental results, the properties of the current cement mixes showed high sensitivity to temperature variations as small as 10°F. To achieve a cement plug as expected, accurate knowledge of the well temperature profile and precise selection of the best additives for such small temperature intervals are necessary. If crossflow occurs, then setting a plug itself can change the temperature profile. This makes cement plug operations even more challenging during actual field practice. The cement mixes were modified and tailored to reduce their sensitivity to temperature without affecting the dump time and strength development. This paper discusses the challenges associated with wireline-run cementing operations and presents a simple and streamlined process developed to help reduce operational time and minimize costs. The study also discusses cement mixes customized for dump bailer operations.
Wireline Tractor for Through-Tubing Intervention in Wells with Barefoot Openhole Completions
Authors: Giem Greg , Sheiretov Todor , Couble Yoann 
Published: March 2018

Abstract
This paper presents the design features and the results from field trials of a new wireline tractor developed specifically for through-tubing intervention into producing horizontal wells with barefoot completions.
Many Middle East horizontal wells have barefoot completions in which the producing zone is left without tubulars. The vertical section is cased and production tubing put in place. Intervention for production logging or remedial work is challenging due to the need to pass through tubing and then operate in open hole. Intervention is conducted on coiled tubing or wireline tractors. Coiled tubing has limited reach in open hole due to higher friction, and it chokes flow through the tubing, resulting in inaccurate production logs. Conventional wheeled tractors apply stress that can destroy some formations at the wheel contact point. This leads to heavy slippage and extremely slow progress.
Several technical innovations were implemented in the new tractor to overcome these challenges. A reciprocating mechanism drives a pair of linked grips with independent opening diameters to conform to variations in borehole geometry while providing a large contact area with the formation. The radial force is hydraulically amplified from the tractor load, enabling it to grip with as much force as required. Results from field trials show little to no slippage in conditions where previous tractors have struggled. The tractor features dual floating hubs that let it close in the uphole direction when tractoring to improve restriction navigation or close in the downhole direction while pulling out of hole to prevent self-locking. The combination of the dual floating hubs and a constant-force opening mechanism enables automatic navigation of restrictions and expansions where previous technologies would have required a manual open/close sequence. These innovations were successfully tested in several tractor operations. One case study is presented in which these features were instrumental in successfully getting to the bottom of the well and back to surface. In one case, the same well was logged using coiled tubing, a prior-generation tractor, and the new tractor. A comparison of these intervention methods is shown.
The integration of a reciprocating tractor drive mechanism with novel technical solutions for linked grips, pad pressure regulation, constant force expansion, dual floating hubs mechanism, and automatic navigation has resulted in more reliable and efficient tractor operation in wells with barefoot completions.
Application of Refracturing Using Coiled Tubing Opens a New Door of Opportunities for Unconventional Reservoir Stimulation
Authors: Pankaj Piyush , Shukla Priyavrat 
Published: March 2018

Abstract
In North America, refracturing has been found to be effective in many instances for increasing the longevity of the well production and helping to drill and complete offset wells. Several instances suggest that refracturing by bull-heading is relatively ineffective because fluids and proppants are lost in the pre-existing hydraulic fractures. Refracturing through coiled tubing (CT) provides a large benefit in giving ability to pinpoint the location of the refracturing treatment by creating new perforations using abrasive jetting and using diversion pills for isolating high-permeability clusters. This paper helps elucidate the benefits and production gain when using CT for refracturing jobs.
A case study from the Eagle Ford shale illustrates the impact of CT refracturing applications. When CT was hydraulic fracturing was applied in the first generation of wells with 18 stages, 36% extra production was observed in the first year as compared to the bullheading technique. Simulations based on integrated reservoir and geomechanical earth models, complex hydraulic fracture models, diversion simulation, numerical production simulation and finite element computations enable characterizing the productivity from the CT refrac operations. A comparison is made between the bullheading technique and CT based refracturing jobs. The impact of refracturing using CT on the offset child wells to be drilled and completed is also studied.
The study demonstrates that it is critical to place the perforation locations in areas of undepleted reservoir for successful refracturing. Reservoir simulation results in combination with measurements of fluid flow profile in the wellbore can be used to place new perforations in the right sections. Using the diversion pill was found to be greatly effective in improving the fracturing fluid diversion and stimulating the undrained reservoir. With the refracturing using CT, the child wells show improvement in productivity along with the parent well. Overall, the parent and child well combination shows 23% increase in production after one year of refracturing when compared to no refracturing in the parent wellbore.
The new approach is verified through the application of simulation and modeling to prove the benefit of CT refracturing operations in unconventional reservoirs. By adopting the key learnings and approach followed in this paper, operators can maximize their chances to improve productivity and compare various refracturing scenarios.
Electric Line Deployed In-Well Rectification of Damaged Completion Components Re-Enables Well Access and Subsequent Intervention, Reinstating Production of Shut-In Wells
Authors: Murchie S. W. , GrØnnerØd A. , Hansen R. , Magnussen O. E. , Tungesvik M. , Hårsaker L. 
Published: March 2018

Abstract
There are wells shut in because of damaged completion components which hinder their production control or integrity, or prevent a remedial intervention from being carried out. Often, the option to pull the completion has inherent risks from an operational, environmental and/or reservoir damage perspective and require extensive resources and time to execute. Rectifying completion component damage through a light but effective in-well intervention solution offers highly valuable options to reinstate production from such wells.
This paper will discuss the rapid engineering development of an expander tool run in conjunction with an electric line deployed electrohydraulic mechanical stroker tool. Through a simple but highly-effective design, an expander tool was engineered to harness and magnify the axial force delivered by the stroker to generate a radial expansion with a force magnitude sufficient to prize out a defect in a completion component. Critical to the design was a precise measurement and control of the expansion extent and the radial force exerted, so the component in question and the other components of the completion were not damaged.
This toolstring combination, coupled with real-time control and surface readout of key tool parameters, enabled a precise and measured high-magnitude expansion capability to be deployed in two different wells with ease, at pinpoint depth, and applied repeatedly across the length of the defect it was addressing. Furthermore, immediate validation of the repair was available through a drift verification pass. In both cases the in-well repair operation eliminated the need for a high cost, high risk completion retrieval and the repair operation was executed flawlessly in hours, enabling the subsequent intervention operations to be carried out and the wells be brought back on line with positive production results.
The tool development was an exemplary case of rapid-response engineering, whose ingenuity stemmed from a direct customer request to solve a challenging completion defect. It resulted in a world first for an electric line deployed in-well expansion solution, the resulting value of which was well acknowledged by the customer.
Rotation and Diameter Growth of Coiled Tubing
Authors: Ken Newman P. E. , Kelleher Patrick , Rain David , Cai Charlie 
Published: March 2018

Abstract
The fact that coiled tubing (CT) rotates when used is not currently included in CT fatigue models. The CT also experiences diametrical growth and elongation. Almost all fatigue testing is done without rotating the CT sample. Diameter growth models based on these fatigue tests have over predicted the amount of diametrical growth.
This ongoing work has already shown that rotation affects the fatigue life. Fatigue life calculations without rotation are usually conservative. It has also shown that rotation does not explain the over prediction of diametrical growth. It is currently believed that the axial force (weight) in the CT causes elongation and a diametrical decrease, which reduces the diametrical growth. It is also possible that the injector chains cause some reduction in diameter. The fatigue/plasticity model being developed will attempt to answer more of these questions. This paper presents fatigue testing with rotation and with varying pressures, which is being used to validate the model. Lab measurements made with a rotation measuring device are also presented.
Successful Coiled-Tubing Cleanout of Heavy Post-Fracturing Proppant in Deepwater Gulf of Mexico: Case History
Authors: Webb J. K. , Sonnier B. 
Published: March 2018

Abstract
Sintered bauxite is the primary proppant used during deepwater Gulf of Mexico (GOM) operations because of its high strength and conductivity. However, the use of bauxite proppant presents operational issues for coiled tubing (CT) resulting from its high specific gravity (approximately 3.6). This paper describes the planning and execution of a heavy post-fracturing proppant cleanout operation using CT in the operator's Tahiti field in the US GOM.
During completion operations on a subsea well, access to the well was provided by a dynamically positioned drillship. After installing the lower completion in the well using drillpipe, a proppant-laden stimulation treatment was pumped. During this process, an early screenout was encountered, and approximately 171,300-lbm proppant remained in the drillpipe that was unable to be reversed out. A CT unit was rigged up in a tension-lift frame that suspended the drillpipe string, allowing for a motion-compensated window to rig up the CT injector head and pressure- control equipment. A 1.75-in. outer diameter (OD) CT string was used to clean out the wellbore to 24,215 ft by circulating brine down the CT string and up and out of the drillpipe through a flow cross.
Preexisting contingency planning proved invaluable for efficient cleanout operations by providing the physical assets necessary to perform a successful operation as well as a framework for the engineering and procedures required. The drillstring was effectively cleaned of proppant to 24,215 ft. Once the well was deemed clean, kill-weight fluid was circulated into the well to allow for further well intervention operations and the eventual return to completion operations.
This case study illustrates the importance of contingency planning to help minimize overall operation costs. The large-scale and challenging well conditions of this unique project led to valuable lessons learned that can be used to optimize performance during future cleanout and drillship operations.
Unique High Pressure Fishing Operation Leads Way to Increased Completions Efficiency
Authors: Skufca Jason , Stabler Christopher 
Published: March 2018

Abstract
Plug-and-perf multizone fracturing remains a dominate completion method in the Haynesville shale. Removing the composite frac plugs (CFP) utilizing coiled tubing (CT) remains a challenging operation with increased risks due to extreme well environments. Operations completed using older, conventional methodologies increase the likelihood of stuck CT events. These stuck pipe events add considerable cost to the completion through fishing, lost production time, or worse, loss of the entire well.
In one such instance while milling CFPs, the downhole tools seized resulting in loss of circulation, subsequently leading to a stuck in hole event. Wireline severing tools cut the pipe in the vertical section, leaving over 4,500 ft of 2 in. CT in the lateral. Removing the CT fish without damaging the formation was paramount to the long-term profitability of the well. Conventional fishing methods were considered, but unfavorable economics in addition to the risk of formation damage lead to the selection of a hybrid approach combining wireline, snubbing, slickline and CT.
The fish was successfully latched using a snubbing unit, providing a conduit for 1-¼ in. CT to convey a severing tool to free the larger coil in the lateral section. This enabled the continuous removal of the 2 in. CT under live well conditions, saving over 4 million dollars and 55 days compared to conventional techniques. Following the stuck pipe event, a complete change in the drillout procedure was implemented, increasing efficiency while minimizing the risk of a repeat event.
Latest Tractor Technology Provides Performance Improvements in Unconventional Shales
Authors: McCutcheon Wade , Long Jarrod , Zambrano Mauro , Sorg Andrew 
Published: March 2018

Abstract
When configuring tractor assemblies for highly deviated or horizontal conveyance, the tractor power required to deliver the conveyed passenger tool to the target well depth is determined by the weight of the deployed cable and payload, the tortuosity of the well trajectory, and the extent of the target depth. Until now, the tractor toolstring needed to be configured accordingly before being run in hole. Conveyance speed is compromised for the maximum power requirements expected to ensure the tractor is capable of delivering the payload to the target depth.
Having the ability to adjust the power versus speed on command allows the tractor to be optimized to deliver the highest speed in the earlier parts of the well where maximum power is not required. In the deeper portions, or where the well becomes more tortuous, the tractor can be controlled to provide maximum power and ensure the target depth is achieved. Real time control delivers considerable reductions in total conveyance operating time. This is achieved by independently controlling the various drive sections to deliver the optimum speed/power configuration per well section.
There have been more than seventy jobs completed to date utilizing selective functionality across a variety of US land tractor conveyance operations. The jobs have been performed with a range of electric line companies while servicing numerous exploration and production (E&P) operators. Examples include record wells with lateral lengths requiring over 15,000 ft of tractoring. The application of this in-well, real-time adjusted optimization has resulted in tractor conveyance time savings of over 40%. In addition to the efficiency gains, there has also been a reduction in operational risk due to less time spent in hole tractoring.
Selective tractor functionality is commercially available from one provider at the time of writing, but it is quickly setting standards for all tractor conveyance providers.
Real-Time Fiber Optic Integrated System Provides Precision and Confidence in a Coiled-Tubing-Conveyed Perforating Operation: A Case Study from the Eastern Foothills in Colombia
Authors: Vera Vanessa , Torres Carlos A. , Delgado Eduardo , Pacheco Carlos , Sampayo David , Higuera Josue , Torres Monica 
Published: March 2018

Abstract
Underbalanced perforating with conventional cable operations involves several risks associated with well tortuosity, cable tension capacity, gun lifting, and the capability of achieving the optimum underbalance for effective tunnel cleanup (Graeme et al. 2008). Because of these risks, an operator in Colombia elected to perform a perforating operation using a coiled tubing (CT) real-time fiber optic (RTFO) integrated system in a newly drilled development well.
CT-conveyed perforating is ideal for this type of wellbore. To achieve the proper underbalance and depth correlation to perforate the target interval, an RTFO CT system provides the most accurate and reliable depth correlation process, in addition to real-time pressure and temperature monitoring inside the CT and the outer annulus.
Using the RTFO CT system, only two runs were necessary to complete the perforating program, in accordance with the operator design, rather than performing an additional run needed for pickling and to generate underbalanced conditions.
The use of the RTFO CT system can help to prevent correlation errors resulting from CT elongation.
A CT structure was not necessary to deploy the guns based on the finite model analysis that calculates maximum stress and flange bending, including a safety factor.
A hydraulic firing head can be used with an RTFO CT system to activate the guns without affecting the integrity of the fiber optics or the downhole sensor tool after detonation.
The RTFO CT system enabled the operator to evaluate the reservoir potential. The evaluation results indicated that one of the zones is a low producer, which avoided the pumping of unnecessary nitrogen to induce the specific zone.
The use of a downhole pressure sensor enabled the identification of the time at which the guns were detonated.
Improvement to the rigup was evidenced and enabled time optimization without affecting the operation.
The casing collar locator (CCL), used for depth correlation, was a crucial factor in reducing operational costs because it helped to optimize placement accuracy and gun detonation and to prevent misfiring (Newman 2003). The guns were successfully activated without nonproductive time (NPT) or health, safety, or environmental (HSE) incidents during operations.
A successful perforating operation was completed with 4,000 psi underbalance in a new formation using hydraulic detonation with continuous real-time downhole condition monitoring before and after detonation, enabling the operating company to make decisions in real time.
This new approach of using an RTFO CT system combined with the hydraulic firing head can be used to perforate new formations in these crucial scenarios (wells with production greater than 20 MMscf/D and zones with continued sand production).
Groundwater quality assessment and its suitability for agricultural purposes in the Behbahan Plain, SW Iran
Authors: Ehya Farhad , Marbouti Zohreh 
Published: March 2018

Abstract
Groundwater is the main agricultural water resource in arid and semi-arid regions, so, preserving it is extremely important. In this study, groundwater quality was assessed for irrigation, using the principal chemical and physical quality parameters from 30 wells in the study area. Groundwater classification on the basis of electrical conductivity reveals that more than 85% of the samples taken fall into the ‘unsuitable’ and ‘doubtful’ classes. On the basis of Richards's classification, 67% of the samples are unsuitable for irrigation. Most, however, appear suitable for irrigation based on their sodium adsorption ratio, %Na, permeability index, magnesium adsorption ratio, Kelly's ratio and residual sodium carbonate water quality indices. The concentration of boron varies between 0 and 2 mg/l, within the FAO's (Food and Agriculture Organization of the United Nations) acceptable standard range. About 60% of the wells are not suitable for drip irrigation because of the water's potential for clogging. There will be no water infiltration problem, if groundwater in the study area is used for irrigation. With respect to the SO42− and Cl− concentrations, 53% and 13% of the samples collected are unsuitable for irrigation, respectively. Less than 10% of the samples have ‘severe’ constraints restricting their use for irrigation with respect to nitrogen. For sprinkler irrigation, however, the groundwater is subject to ‘severe’ restrictions. Geochemical investigations indicate that the water chemistry is affected by processes including evaporation, water-rock interactions and human activities.