High-rate, multistage hydraulic fracturing in unconventional wells results in high internal burst loads, which are normally considered during production string design; yet, recent production casing failures exhibit casing collapse after several stages of a fracturing operation. Post-analyses of presented case studies demonstrate that production strings can be exposed to high-fracturing collapse loads caused by inadequate cement bonds around the casing. In this study, a fracturing operation was initially simulated to obtain an actual thermal profile for casing-stress analysis with a thermal wellbore simulator. Based on available data, bottomhole treating pressure (BHTP) was calculated to match the actual field data. A load case was run to check the collapse integrity of production casing with the assumption that a casing section below the top of cement (TOC) is fully exposed to the simulated BHTP because of channels created in the casing annulus. Additionally, a sensitivity analysis was performed to identify the threshold BHTP limit that can start collapse failure. Another scenario was simulated by assuming a good cement bond for comparison with previous simulations. Two case studies are presented wherein production casing collapse failures occurred during multistage fracturing operations. Both wells had horizontal trajectories and planned for 20 and 28 frac stages, respectively. Results based on actual field data demonstrate that the collapse safety factors were less than the design factors all the way from TOC to the casing shoe depth in case of exposure to BHTP in the casing annulus. Additionally, the sensitivity analysis highlighted that the casing collapse rating can be exceeded if exposed to even lesser BHTP than simulated and actual BHTPs. Simulations without any pressure communication to the annulus also confirmed that the potential of collapse failure becomes minimal with adequate cement bond under multistage-fracturing operations. Based on these findings, it was derived that casing collapse failures in both wells were the result of BHTP transfer into the annulus while fracturing operations. Such failures could be avoided in the future with additional design considerations during the planning phase of such wells. This work shows the importance of additional collapse loads for production strings to improve the integrity of unconventional wellbores that are designed for multistage hydraulic fracturing operations. It is possible to ignore this load analysis if all potential operational risks are addressed with appropriate contingency designs.
Scale-squeeze remediation has been used extensively for removing scale from production strings in offshore and deepwater environments. During scale remediation treatments, the affected tubulars undergo displacement and stress that can affect the effective seal length and integrity of the completion system. Numerous laboratory simulations can be performed to help determine the effectiveness of the treatment fluids, injection volume, scale-inhibitor retention time, fluid composition, and shut-in time; however, sufficient research has not been conducted regarding the effects of these important parameters on the structural integrity of completion systems during an actual scale-inhibition squeeze treatment. This paper studies the effects of these important parameters on completion system integrity by (1) performing wellbore thermal simulations of the treatment operations, (2) investigating how much tubing movement has occurred during these operations, (3) analyzing stress on the tubulars during different operations, (4) investigating the effects of scale-inhibition application methods on tubing movement, and (5) recommending a fit-for-purpose tubing movement workflow for the scale remediation process based on laboratory and field data. This paper investigates six cases using data from a Gulf of Mexico deepwater well. The parameters studied include injection rate, injection pressure, shut-in "soak period" time, and volume of injected treatment fluids. The results show that shut-in time, injection pressure, and injection rate are sensitive parameters that can significantly affect tubing movement and wellbore stress on tubulars. The method of application by means of squeeze treatment or continuous pumping is proven to be an important requirement for these types of operations and should be seriously considered when designing scale-squeeze treatments. These findings also provide the necessary information for optimizing the design treatment, developing good completion spaceout and design, as well as improving operational procedures for scale-remediation applications.
Special Section: The Value and Future of Petroleum Engineering JPT asked several active young professionals about their career path thus far and what they liked about petroleum engineering. Here are some of their answers. Feeling Lucky Carter Clemens, BP I lucked into the petroleum industry; I did not know much about it before choosing it as a major at the University of Texas. It has allowed me to live and travel to distant countries I never thought I would visit—whether it is Abu Dhabi, Port of Spain, Cairo, or Aberdeen, the oil industry has an incredible reach to some interesting locations. It has also enabled me to pursue engineering while spending a lot of my time outside instead of in front of a computer screen. When I was riding around with well operators in Wyoming and Colorado, I thought of how lucky I was to not be in a cubicle. There is something special about being on a well-site surrounded by snow in Wyoming or watching a sunrise from a rig in the middle of the ocean—you can’t get that with most industries. Personal Satisfaction Bruno S. Rivas, Mexico National Hydrocarbons Commission Petroleum engineering is more than get-ting oil out of the ground; it means delivering the energy that the world needs to fight poverty, increase human wellness, and accelerate growth in a sustainable way. The oil and gas industry has given me the opportunity to interact with professionals from all over the world, to exchange different experiences, to solve problems in a responsible and efficient manner, and to inspire future generations. With no doubt, if I had to decide again what to study, my choice would be oil and gas; it is certainly not an easy path, but realizing that I’m generating a positive impact on others’ lives is a personal satisfaction. Let’s Talk Climate Change Angela Dang Atkinson, Encana Corp. I love saying, “I’m a petroleum engineer and I believe in anthropogenic climate change.” It catches people off guard and begins a nuanced conversation about energy. It is an opportunity for me to talk about the importance of incremental change and that there is no silver bullet in solving the world’s energy challenges. As Harvard economics professor Ed Glaeser states, “Once we start thinking that there’s a silver bullet…we lose the fact that we need to be working day by day, over decades, to effect change.” We, the oil industry, are among those working day by day to effect change—whether we are increasing the use of recycled fracture water or finding creative ways to reduce emissions, these are the types of incremental gains on the way to better energy solutions. This nuanced conversation should not primarily exist in 150-character tidbits online. It is up to us to have that conversation in a grassroots manner, face to face, with our community.
Forum This year and the last have been significant for acquisitions in the energy sector. At the corporate level, we are seeing the Halliburton takeover of Baker Hughes, the Shell buyout of BG Group, and Repsol’s acquisition of Talisman. At the asset level, there was the Woodside-Apache liquefied natural gas project, Nigerian companies’ acquisition of western companies’ interests in the country, and various master limited partnership mergers in the US. The TWA Forum team talked with some of the top minds in the energy mergers and acquisitions (M&A) arena about what is driving the market, and how to prepare yourself if you are employed on either side of a transaction. This article will provide an overview of what happens behind closed doors before a merger or an acquisition takes place. What Gets the Ball Rolling? What are the key drivers of M&A activity in the energy sector? Alan Tambosso (AT): The key drivers are currently cash flow, cash flow, and cash flow! Assets that are currently making money are in demand. Previously, assets were traded on a reserves basis. Transactions were very often based on a proved plus probable reserves value at a specified discount rate, say 15%. However, the focus has changed now as the market demands a current cash flow. The shift in M&A drivers from reserves to cash flow occurred in the early 1990s when junior companies would buy underdeveloped assets with lots of reserves and then put capital in to accelerate the cash flow of the asset. This in turn provided more capital to develop more reserves, which created growth. The market reacted by funding these companies, as markets will always allocate capital toward companies with high growth potential. Recently, low commodity prices have highlighted the focus on cash flow. Assets must be producing positive cash flow or the company holding the assets will not be able to sustain itself. Other drivers of transactions are debt, including operational obligations, such as abandonment liabilities. Companies with high levels of debt are less likely to be able to acquire a company or asset. In addition, acquirers may not want to purchase a target with high debt load.
In the last two decades, oil and gas operators and service companies are moving towards a more proactive rather than reactive mode in the drilling process optimization following the use of remote operating centers (ROCs) for rapid problem identification, assessment and mitigation. The methodologies adopted may be different across companies or regions but the underlying objective for most is to drill wells efficiently in a cost-effective manner. In spite of the rapid and continuous development of real time monitoring protocols, there are still gaps in the use of these aggregated data and information obtained from ROCs to achieve fully integrated drilling process modeling and optimization in real time. The paper highlights the importance of a full-integrated approach to using real time drilling engineering and optimization methodology in order to gain valuable insights that allow operational teams to execute wells with minimal non-productive Developing a functional real time drilling engineering methodology requires several years of failing fast and evolving towards a more improved performance organization where preemptive actions can be taken before problems occur. The methodology begins with performing full-integrated geomechanics study to understand the underlying geological uncertainties, stresses and faulting regimes within the area. The results from the geomechanical study form the basis for the detailed design of the casing, mud, cement, drillstring as well as the interaction of all these artifacts in order to develop operating parameters for well execution. Detailed drilling engineering road maps along with its associate risk matrices are developed to determine the operating ranges and bases of monitoring. During real time execution, these models including the 1-D geomechanical model, BHA design & modeling, casing design, fluids design, cementing design are updated continuously as more data become available in real time. The real time drilling engineering analysis coupled with integrated in-house and real-time center (iROC) personnel, 24/7 support provides immediate recommendations that can eliminate and avoid potential undesirable drilling events such as stuck pipes, lost circulations, and downhole tool failures. By applying this integrated methodology in the Gulf of Mexico, a significant improvement in technical efficiency and by extension the operational efficiencies in performance through implementing same goals(s) focus, objectives aligned with collaborative planning, integrated 24/7 real-time operations support and solutions, execution and delivering correct and detailed communication protocols with united focal points across multiple stake holders. This resulted in completed well construction phase eight days ahead of schedule, with zero safety incidents. This study validates the value of integrated services approach with focal point leadership using the right communication protocols with 24/7 monitoring and proactive support, improves the efficiency of the well construction process and ultimately lowers the cost and/or increases the production output of the project.
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