Well Abandonment

Cemented casing sections were recovered from the upper part of a Norwegian North Sea production well during a permanent abandonment operation. The barrier quality of the cement sheath, which has been sandwiched between two casing strings for more than 30 years since the well was constructed, has been investigated. Measurements recorded using acoustic logs, fluid leakage testing, and core plug analysis are evaluated, and the results are presented. Two sections were selected from those recovered during well abandonment, the deepest from approximately 260 m depth and a second from the interval covering the top of cement (TOC). The leakage properties of these sections were measured using water and nitrogen. Core plugs were recovered from the top and bottom of each section and petrophysical, chemical, and mechanical properties were measured. The casing ends were sealed with pressure-tight bulkheads enabling acoustic logging to be performed under pressure. The sections were logged at their initial condition: "dry", as delivered onshore and thereafter "wet" after attempting to saturate them with water. Initial leakage testing with nitrogen enabled the distribution of the fluid leakage paths through the ends of each section to be visualized. The leakage path properties were observed to vary axially along each section and also for different positions around the azimuth of the outer casing. The acoustic logs were analyzed and provided a detailed map of the axial and azimuthal variations of the cement bonded to the inner casing of each well section. The variation of the log response recorded under dry and wet conditions was correlated with the leakage property variations measured along and around the casing sections. The log response was found to be consistent with the physical observations and leakage test results. The presence of microdebonding between the casing and cement and the transition to mud solids and fluid pockets above the top of the cement were readily observed. A unique and comprehensive data set has been acquired comprising acoustic logs and laboratory measurements of water and gas leakage rates and cement properties, recorded on casing sections retrieved after more than 30 years of operational exposure downhole. The measurements enabled the cement log analysis to be compared directly to physical measurements of the well barrier quality.

There is a large number of subsea production wells offshore Norway approaching the end of their lifetime. Considering high spread rate of semisubmersible rigs, abandonment operations of these wells will be quite expensive. Moreover, Plug and abandonment (P&A) can easily contribute with 25% of the total costs of drilling for exploration wells offshore Norway. Hence it is of great importance to seek approaches and solutions to reduce the P&A cost. This paper reviews some possible new ways and also alternative technologies as the solutions to cut down the P&A expenses. Some of these technologies are now being used offshore Norway.In the first section of this paper, challenges of performing P&A operations offshore Norway together with the main cost drivers are discussed. It is then briefly argued how to consider issues such as barriers setting depth, cementing depth and logging in the design and well construction phases to ease or avoid future P&A challenges. For hydrocarbon exploitation in the Barents Sea and Arctic regions it is important to take into account the P&A phase in the early stage of planning and development.Light well intervention vessels as alternatives to semisubmersible rigs are recognized of being the largest contributor to cost saving. It will then be discussed to what extent vessel technologies can cut down the expenses for subsea abandonment. New ways of performing P&A can be another contributor to cost saving. It is shown how research and testing can assure the operators of new ways for performing P&A. Retrieval of production tubing is a challenging suboperation such that it imposes significant cost to subsea well abandonment. There have been performed studies on how P&A could be performed with tubing left in hole and it is of interest to pursue this further. We will investigate how the abandonment operations can be simplified and be more cost efficient if the production tubing can be left inside the well where the basic assumptions for being able to do it is accounted for.In addition, some complexities in abandonment operations can cause additional cost. An example of such complexities can be the need to establish two permanent barriers for potential permeable zones in overburden. It will be demonstrated how much can be saved with respect to cost if the regulations allow to ease some parts of abandonment operations.In this study, a probabilistic approach as a systematic tool to produce unbiased results is applied to quantify cost savings of new alternatives compared to the traditional ones.© 2015 ASME

When subsea fields are reaching the end of their productive lives, the aging assets will need to be decommissioned, of which the well abandonment operations can amount to two thirds of all decommissioning expenditures.  Therefore, reducing the cost associated with this activity, without compromising safety is the premium goal owners are pursuing, especially with the current economic climate and low oil prices. It is imperative for the industry to explore and expand the current approaches in order to shrink the bill, of which can include: new strategic thinking; new methodologies; and the development of new and innovative technologies. To assist the industry in finding the most cost effective solutions in the offshore well Plug and Abandonment (P&A) area, DNV GL recently released a guideline for the risk based approach to plug and abandonment of offshore wells, which provides an alternative approach to the current access abandonment design. This paper presents the challenges of offshore well P&A in the Gulf of Mexico, the possible approaches to address these issues, and describes how the DNV GL guideline can be used for offshore well abandonment activities.

Well abandonment is often not thought of as a crucial part of a well’s life. As such, traditional methods of abandoning a well utilizing cement and bridge plugs are still common practice among most operators throughout the world. Although resins have been utilized by some as an alternative, there have not been anymajor new developments in well abandonment materials for nearly 100 years. Although each of these materials have their benefits, there are also limitations to their sealing capabilities. Bridge plugs lack a high expansion ratio required in some wells and rely on elastomers to seal, limiting their ability to seal in damaged tubing or open hole environments. Cement is porous and lacks the ability to block gasses from migrating through it. Resins must be squeezed into an area and can take days to fully cure before a seal is created. This paper will demonstrate 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 introduces a BHA with integrated casing cutting and fishing tools applied in offshore operations of well abandonment. This kind of tool systems successfully applied in an offshore project of permanent abandoned wells. The advantage of the system is the combination of both cutting and fishing operations, and thereby the completion of the both operations implemented in one string tripping. The benefit through the application of this novel combination could be of reducing numbers of make-up of BHAs and tripping. Therefore, the operation process is simplified, and the operation efficiency and reliability are significantly improved.

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper OTC 29839, “Successful Offshore Coiled-Tubing Permanent Well-Abandonment Operation Uses Downhole Real-Time Parameters To Set Inflatable Packers With Surgical Precision in Cost-Effective Manner,” by Cassiano Guimaraes, Eduardo Delgado, SPE, and Lucio Galvao, Halliburton, et al., prepared for the 2019 Offshore Technology Conference Brasil, Rio de Janeiro, 29-31 October. The paper has not been peer reviewed. Copyright 2019 Offshore Technology Conference. Reproduced by permission. The complete paper discusses the systematic approach adopted by a service company to achieve the goal of safely abandoning wells offshore southwest Brazil with different completion types using light workover vessels. Having determined the abandonment methodology, service company personnel developed processes and procedures to reach the objective that included advances in coiled-tubing (CT) rigup procedures and use of a real-time telemetry system. Introduction The use of a CT real-time telemetry sys-tem enables accurate setting of a through-tubing inflatable device system (T-TIDS) by monitoring the necessary downhole parameters in real time. The paper presents a case study wherein sensors [such as a casing collar locator (CCL) to perform depth correlation before setting the T-TIDS and placing cement plugs, a pressure sensor to monitor the T-TIDS setting, and a CT internal pressure sensor to help ensure all cement was pumped out of the CT] were used in real time to verify that well barriers were set in place, contributing to successful well abandonment. Real-time data collection proved to be the most-effective methodology for running critical equipment, thereby saving overall time and cost. General Abandonment Requirements The decision for permanent abandonment of a well is not always easy. In Brazil, the National Agency of Petroleum, Natural Gas, and Biofuels (ANP) has established a compendium of rules for oil companies that extract and produce oil, gas, and derivatives. This involves a group of barriers known as CSB, which is a set of one or more elements with the objective of preventing the unintentional flow of fluids from the formation to the external environment and between intervals in the well considering all possible paths. The CSB’s aim is to guarantee the isolation of intervals with current and future flow potential. Cement or other material with similar performance must be used as barrier elements. Achieving a unique solution is dependent on having up-to-date information regarding the wellbore diagram, reservoir, history, well location, CT-performance capability, surface equipment, well-control equipment, and proposed layout. Fig. 1 illustrates the design of the 3D wellbore graph generated with modeling software. Solution Described The well discussed in this work contains deposits of asphaltene and sand-accumulation debris. For the operator to perform a plug-and-abandon (P&A) intervention, an effective solution to provide reliability safely is necessary to avoid worsening the well condition and delaying the intervention. The service company offered experienced personnel and engineering capabilities, a customized program for job-specific requirements, the CT package, and reliable processes and advantages compared with heavy workover units. Included as part of those advantages is a variety of bottomhole-assembly (BHA) tools that can be deployed in the well with the capability to be customized, working together with wireline operations and the robust management safety system.

Shutting the aging well for good towards the end of field life requires a lot of operational and technical considerations as well as high cost to ensure project viability and safe operation. Procedures to evaluate competent cap rock layers as natural formation barriers, well plug and abandonment (P&A) design, assurance on well barrier integrity through cement bond logging and best practices in well abandonment will be highlighted through three case studies in this paper. Data integration starting from the early exploration or development drilling phase, during production and towards the abandonment phase play key roles in the project and will be the ultimate pinnacles in determining cap rock intervals, cement integrity, tubulars condition, potential reservoir communication and plug setting depth in the well. Adding an extensive behind casing acoustic noise, pulsed neutron and cement bond logging campaign and full integrated formation evaluation in the picture will further enhance the feasibility of abandonment project with additional discovery of shallow gas potential to prolong the field economics. Detail analysis of petrophysical logs, mud log gas reading, well pressure monitoring, shallow gas hazard site survey and acoustic-noise log deliverables have revealed the presence of shallow gas as deep as 300-400 m below the sea bed and few more intervals at deeper or shallower depth. Incorporating all available data to date had resulted in extensive volume of gas-in-place being evaluated, thus driving additional value through potential workover or shallow gas appraisal project prior to abandonment. In addition, operational cost, time and safety will be further optimized through cap rock restoration method and cement recipe upgrading. In a nutshell, packaging shallow gas potential and possible work-over or appraisal campaign for quick field monetization prior to abandonment will prove to justify the project economics. Changing the game from conventional gas producer to shallow hanging fruits opportunity is worth to be exploited in this case.

Typically, most of the well abandonment practice is reference to the recognized industry standards i.e. NORSOK, UK Oil & Gas and etc, and this is how the wells abandonment was carried out in the past. These practices however evolved/changed over time with lessons learnt and experiences and turn into a fit for purpose solutions for the Client. The shift in international and local standards and regulations for a robust plug and abandonment approach has placed the need for a better and long lasting permanent P&A methodology. Adhering to the existing industry standards in well abandonment is somehow not practical and not cost effective to be implemented in different part of the well, where there are major differences in local regulations, reservoir conditions, caprock thickness, well design philosophy and etc. The magnitude of abandonment cost increase is not at par with the risk reduction in long term hydrocarbon leakage. A fit for purpose solutions is recommended in closing the gap between cost and risk. Due to the extremely varied well architecture between wells, the approach to permanent abandonment varies depending on casing sizes, presence of packers and no of casings present to the caprock area. On top of that, identifying the highest depth for a placement of cement plug will reduce on the amount of plugs to be placed, saving rig time and operational time. So far, 16 idle wells have since been permanently abandoned with the systematic approach of applying caprock restoration concept and reinstating the poor isolation across caprock areas with cement with the assistance of technology to the likes of perf-wash-cement, and hydro mechanical casing cutter. These wells have successfully been abandoned as per host authority standards. This paper will explore a major local oil company’ approach to decommissioning of wells, in line with local regulations enforced, while ensuring a cost effective approach is applied in line with the available technologies.

Discuss a cost-effective rigless methodology to abandon complex onshore wells. –Onshore wells can be near housing, and multiple non-technical risks (NTR) need to be carefully managed to keep the license to operate.–Select a 100% electric rigless plug and abandonment (P&A) unit to reduce emissions, smell, and noise contour.–Manage and execute a complex P&A scope of work of 60+ wells in three years. This paper studies the solutions selected and implemented by the project management team in collaboration with the well operator for a successful start-up and cost-effective well abandonment project. –Implement the first fully integrated well abandonment project solution for onshore P&A in the Netherlands including well P&A services, hydraulic workover (HWO), logistics, and site preparation.–Ensure full compliance with the stringent local mining and environmental regulations.–Select a bespoke P&A unit to provide a robust solution for complex P&A work.–Select downhole services and technologies to successfully execute a complex, rigless P&A work scope. The project encompasses over 60 wells on 23 different onshore locations drilled over a 50 year period. The known scope of work and requirements of multiple contingencies while managing NTRs resulted in the selection of a rigless well abandonment solution. –A modular, highly capable rigless well abandonment unit in combination with enabling downhole technologies provides a total solution for simple and complex wells.–A 100-percent electrically powered P&A unit reduces emissions, smell, and noise contour. This was thefirst electrified P&A unit in the history of the operator running on grid power. All well site equipment is electrically powered (HWO P&A Unit, Mud/Cement Pumps, and ancillary equipment) to reduce emissions, smell, and noise contour.–Project management and engineering is key to ensuring efficient planning and close collaboration with the well operator's project team.–Collaboration between partners enables multi-skilling and reduction of POB to save additional costs.–Improve efficiencies and execution through extensive after-action reviews and learning curves.–Successfully execute complex P&A work and re-establish annular cement integrity on multiple complex wells (perforate, wash and cement, section milling, perf, circulate and cement)–More than 40 wells completed in two years, and operations continue today.–This is the first fully integrated well abandonment approach that includes full project management, well-site supervision, cross-product services, and extensive third-party management (HWO, logistics, and other third-party service companies).–A 100% electric P&A unit reduces emissions, smell, and noise contour, delivering a net reduction of CO2 through electrification.

This paper discusses a systematic approach adopted in order to achieve project objectives during a recent platform well abandonment campaign. An integrated team, comprised of key service company personnel working in conjunction with the oil company with the oil company operations and cementing research staff, developed and implemented innovative procedures and cement slurry designs to support the deployment of coiled tubing. This facilitated the subsequent timely and cost effective field operation to abandon 13 wells in a safe and environmentally sensitive manner.