This paper describes the process followed to explain the mechanical blockage in the flow path observed while displacing the cement slurries in long casing strings set with short rat holes. In most of the cases, those blockages ended with amount of cement left in pipe and significant remedial works.
All the incidents were investigated involving casing design experts, cementing specialists and data analysts to understand the root causes. Mud logging unit, cementing and rig sensors data from several cementing jobs were analyzed in an integrated and holistic approach. Four different software’s were used to simulate and prove the theory that total elongation of the casing was enough to exceed the rat hole length bringing the casing in contact with the bottom of the well, and therefore blocking the flow path.
In all the incidents, the issue was observed at the beginning of the slurry displacement stage where the entire volume of the cement was still inside the casing. Other possible causes of blockage (cement contamination, mechanical failures, loss control material,…) were also checked and ruled out.
Hookload data was available to be analyzed whenever a conventional wellhead was installed, and the casing was held on the elevators during the cementing job. However, in some cases this information was not available as a compact wellhead was used. For those cases, it was necessary to drill out the shoe track using LWD to detect the location of casing shoe.
Recommendations were made to add new loads the current casing design. Results will define the minimum rathole length and the maximum tension at surface experienced by the casing during the cementing job in both static and dynamic conditions. Also, it is important to properly estimate the rathole the physical measurement of the casing joints in the tally can carry measurement errors.
Labrousse, Sébastien (Schlumberger) | Guner, Hakan (Equinor ASA) | Kauffmann, Carlos (Equinor ASA) | Caycedo, Alberto (Schlumberger) | Opsahl, Jørn (Tomax AS) | Atallah, Rawad (WWT International Engineering Services) | Hatleseth, Tore Andreas (KCA Deutag Drilling Norge AS) | Moldekleiv, Rune (Schlumberger) | Nokland, Magnar (Schlumberger) | Andreassen, Ørjan (Schlumberger) | Nyborg, Benjamin (Schlumberger)
The purpose of the paper is to present how an integrated solution was designed to turn a challenging 6-in. section into a successful 6-in. production sidetrack in Norway. A threatening casing wear issue caused by the combination of slow progress and localized dogleg was addressed successfully with a complete redesign of the drilling system.
A 6-in. pilot section suffered slow progress due to low rate of penetration and tool failures. Significant amount of metal swarf was recovered while drilling. A casing wear log quantified the wear in the 9 7/8-in. casing, and this led to questioning the feasibility of the planned 6-in. production sidetrack. Operator, rig contractor and integrated services provider worked together to find a solution.
First, a detailed study of the wear was performed. A wear log was run, and the casing wear was quantified. Casing wear simulations were then calibrated based on wear logs and it appeared feasible to drill the 6-in. sidetrack if a minimum rate of penetration and a maximum number of revolutions were respected.
Second, the drilling system was optimized to ensure faster progress. This was done thanks to the learnings from the pilot section. The mud system was changed, and a lower density was used to increase the rate of penetration. The drillbit was optimized based on the limited wear seen in the bits used in the pilot section. As it was more aggressive, the perceived risk of downhole tool failure was mitigated with the use of an anti-stall tool.
Finally, to reduce the incremental wear from the sidetrack operation, casing protectors and lubricants were run. Also, the planned drillpipe was changed to a lighter drillpipe to reduce the sideforces.
The new system resulted in a successful drilling and section TD was reached ahead of the estimated perfect time.
With this paper we provide a detailed example of how a casing wear issue was addressed. The drivers we extract from this case are useful for the planning of future operations, especially in extended-reach wells.
Moiseenkov, Alexey (Petroleum Development Oman) | Smirnov, Dmitrii (Petroleum Development Oman) | Mahajan, Sandeep (Petroleum Development Oman) | Al Hadhrami, Abdullah (Petroleum Development Oman) | Al Azizi, Issa (Petroleum Development Oman) | Shabibi, Hilal (Petroleum Development Oman) | Balushi, Yousuf (Petroleum Development Oman) | Omairi, Mahmood (Petroleum Development Oman) | Rashdi, Mansoor (Petroleum Development Oman)
There have been many oil and gas field discoveries in the Cambrian Ara Group intra-salt carbonate rocks in the South Oman Salt Basin. These carbonates represent self-charging petroleum system with over-pressured hydrocarbon accumulation in dolomitized rock encased in the salt. Drilling and completion wells going through salt is challenging. Salt creeping behavior results in issues of stuck pipe during drilling operations, casings deformation and collapse that have led to well suspension and abandonment.
The full set of the available historical data analyzed to identify magnitude and history of the problem. The study conducted to estimate of salt creep magnitude, to assess the effect of the salt creep on cement quality, drilling and completion risks. The risk of salt creep on the drilling, completion and long-term well integrity was evaluated with multi-disciplinary integration of geological, geomechanical, petrophysical and well engineering aspects to minimize and mitigate the salt creeping risks. In addition to identify root cause for completion failure and providing recommendations to drilling practices, cementation and completion design that can improve well delivery process.
Salt creep behavior presents drilling challenges associated with excessive torque, stuck pipe, casing deformation, and poor cementing job. Salt creep associated risks to drilling and well integrity should be managed and mitigated. Key study findings captured for wells designs were: Salt creep rate increases with depth, salt thickness and differential stress (function of MW) Non uniform loading decreases the collapse rating of the casing and results in casing deformation Non-uniform loading likely due to poor cementing, interface between rigid carbonate intervals and salt, and irregular open hole quality.
Salt creep rate increases with depth, salt thickness and differential stress (function of MW)
Non uniform loading decreases the collapse rating of the casing and results in casing deformation
Non-uniform loading likely due to poor cementing, interface between rigid carbonate intervals and salt, and irregular open hole quality.
Studied casing collapse cases could likely be attributed to several factors or combinations of factors such as salt mobility behavior, drilling with low MW, poor cement jobs and loss of internal hydrostatic support for the casing after cement job between liners lap. The improved multi-disciplinary understanding of salt creep is vital to reduce drilling and completion costs, unnecessary well abandonment and achieve good life cycle well integrity i.e. avoid extra side-track and workover cost due to integrity issues. The best practices and conclusions summarized in the study for drilling and completion design expected to benefit the exploration and development projects for the salt encased carbonate reservoirs around the globe.
Research and development drives success in shale plays throughout the world, enabling operators to deploy new drilling, completions, and production technologies to reach more reservoir area and extend the life of production wells. This work demonstrates the development, validation, and deployment of an extreme torque casing connection addressing technical challenges of tubulars in unconventionals.
Throughout the well lifetime, Oil Country Tubular Goods (OCTG) experience various loads during the installation, stimulation, and production phases. Some of the challenges experienced during the stimulation and production phases relate to internal and external pressure resistance, sealability, corrosion and cracking, erosion, and wear. Furthermore, with the increase in lateral length and the more demanding well geometries, the OCTG capabilities related to high cycle fatigue, connection runability, and torque limits become more important to safely and efficiently reach the total depth of the well and ensure integrity throughout well life. Another scenario in which the torque limit of an OCTG connection is important is rotating while cementing, a practice undertaken to mitigate sustained casing pressure, improve well integrity, and completion efficiency.
We present the key elements in the development of a casing connection that overcomes these challenges and the decision process leading to a prototype. To prove the design concept, a fit-for-purpose testing protocol was adopted to validate its performance, replicating the installation, stimulation, and production phases under the expected loads. Once validated, a pilot involving casing installation, rotation while cementing and stimulation was completed in two wells, and its outcomes will be discussed in this work.
This novel casing extreme torque connection, designed to overcome the application challenges, enables the installation of casing in longer laterals, together with the improvement of well integrity through rotation while cementing.
The performance of the product, tested through a special procedure while ensuring reliability, was confirmed by the case study from the Niobrara shale. A new connection considering the challenges of wells in unconventional plays must account for several aspects from design to installation. We show the process, from the design stage and validation, leading to successful field deployment.
Ghanavati, Mohsen (Global New Petro Tec Corp.) | Volkov, Maxim (TGT Oilfield Services) | Nagimov, Vener (TGT Oilfield Services) | Ali Mohammadi, Hamzeh (University of Calgary, Global New Petro Tec Corp.)
Production casings of Cyclic Steam Stimulation (CCS) or steam-assisted gravity drainage wells are exposed to significant temperature variations which in many cases resulted in casing breaks in the weakest part which are typically connection joints. The paper focuses on the new downhole logging approach, in monitoring and detecting production casing connection breaks through tubing without requirement for tubing retrieval.
The metal well barriers can be assessed by utilizing electromagnetic (EM) pulse defectoscopy. This is done by running multiple coaxial sensors downhole in tandem. Each sensor generates EM pulse and then records EM decay from surrounding metal tubes. Modeling of recorded EM decay enables precise assessment of metal loss or metal gain in up to four concentric barriers. However, the tool had never been used previously to detect minor defect features as casing breaks through the tubing. To identify casing breaks several yard and field tests have been conducted and new methodologies were developed. The last one included the recognition of specific patterns of raw EM responses, analysis of hole sensors and utilization of data from all coaxial sensors utilized during the downhole survey.
The new approach including downhole EM pulse tools and new data analysis have been implemented to detect casing connection breaks in over a hundred Cyclic Steam Stimulation (CCS) and SteamAssisted Gravity Drainage (SAGD) wells. The paper demonstrates the testing of the application feasibility in a comprehensive yard test and extends to real field examples. All detected breaks were confirmed after tubing removal and were successfully repaired. Paper highlights detection challenges due to different casing connection break types: minor breaks, partial breaks (contrary to fully circumferential), and casing breaks aligned with tubing connections. The technology has helped Operators to fulfil the objectives of connection break detection without tubing removal through a non-intrusive, safe, quick and economical approach.
Today, CSS and SAGD Operators should confirm casing integrity repeatedly prior to each subsequent steam cycle through the time and resource consuming approach of tubing removal and checking the casing integrity mechanically. Utilizing through tubing electromagnetic diagnostics, enables Operators to pick up multiple casing connection breaks in a single run without tubing retrieval.
In this paper, the application of a real-time T&D model is demonstrated. The process of T&D analysis was automated, and the time and cost required to run physical models offline was reduced or, in some cases, eliminated. Precise casing-wear prediction is important for improving well integrity and longevity, while simultaneously making casing designs more cost-effective. There are no industry guidelines for casing-wear prediction. This article presents a validated predictive model.
I am encouraged that we, as an industy, continue to refine and tweak our practices to solve zonal-isolation and cementing challenges in every well environment in which we work. As cementing techniques are improved, so, too, are the cement-evaluation methods and work flows. This paper demonstrates a new way to create gas-tight seals during well abandonment, overcoming the limitations of traditional methods and reducing the operator’s liability and potential environmental impact after decommissioning has been completed. This paper discusses shale creep and other shale-deformation mechanisms and how an understanding of these can be used to activate shale that has not contacted the casing yet to form a well barrier. Well RXY is located in Cairn’s Ravva offshore field in the Krishna-Godavari Basin in India.
Content of PetroWiki is intended for personal use only and to supplement, not replace, engineering judgment. SPE disclaims any and all liability for your use of such content. A continuous string of casing, usually cemented over at least part of its length and usually extending back to surface from the set point.
Content of PetroWiki is intended for personal use only and to supplement, not replace, engineering judgment. SPE disclaims any and all liability for your use of such content. A pressure test of the casing seal, after the cement job, to the pressures necessary to safely control the pressure of the deeper zones.