Cheatham

SPE ATCE and DSATS

The 2011 SPE Annual Technology Conference and Exhibition (ATCE) will convene in Denver from 31 October through 2 November. This event offers many wonderful opportunities for members to learn about technology and make valuable industry contacts. From technical sessions to plenary sessions to the exhibits, there are ample avenues for curious minds to stretch their boundaries. There are also activities even before ATCE officially starts, including training courses, a workshop for Technical Editors of SPE journals (including SPE Drilling & Completion, of course), and meetings of some SPE Technical Sections.

If you are like me, then you may be wondering what exactly a Technical Section is. How many are there? And what do they do? Some research on the SPE Communities website revealed the following information.

First, what is a Technical Section? "A Technical Section is a group of SPE members with a common interest in a technical area who join together to share ideas, promote competence, and develop projects related to their technical interest."

Second, how many are there? Currently SPE has six Technical Sections:

• Digital Energy
• Research & Development
• Wellbore Positioning
• Drilling Systems Automation
• Production & Operations
• Well Integrity

Third, what do they do? Technical Sections generally meet "virtually" but also hold face-to-face meetings once a year. They are global, self-operating groups with officers and members who publicize their section’s technical interest and develop projects to advance the state of the art. They are open to any SPE member to join at no charge.

The newest SPE Technical Section dedicated to drilling or completions activity is the Drilling Systems Automation Technical Section (DSATS). According to its website, "The objective of this group is to accelerate the uptake of drilling systems automation by supporting initiatives that communicate the technology, standardize its nomenclature, promote lessons learned/best practices, and help define its value proposition."

DSATS has had numerous meetings since its inception in 2007. This year, there are two meetings planned, both in conjunction with major SPE conferences. The first meeting was held in Amsterdam in conjunction with the SPE/IADC Drilling Conference and Exhibition last February. The turnout was 270 attendees, which indicated keen interest in the technical area.

The second DSATS meeting in 2011 will be held on 30 October in conjunction with ATCE. The event will include a panel discussion on the expansion of well construction automation beyond drilling into completions and interventions. Heretofore, DSATS has focused on drilling systems, as one would expect from the name. Broadening the discussion to nondrilling activities is expected to draw a large audience from the multidiscipline audience that attends ATCE. Who knows where this meeting might lead the industry? Perhaps one result could be a seventh Technical Section. The meeting site will be the Colorado Convention Center, which is also the site of ATCE. There is no charge to attend this meeting, but you must register to attend because of limited seating.

DSATS has seen strong growth, as demonstrated by its current size of 187 members. Another sign of growth has been the recent formation of a European subcommittee for DSATS. Its purpose is to support and participate in meeting activities in Europe. This geographic expansion indicates the growing global interest in automation.

I encourage you to go to the following website and consider joining one or more Technical Sections: http://communities.spe.org/TechSections/default.aspx.

Now to the papers. Continuing our custom since March 2010, this issue contains 14 papers.

• Carbon capture and storage, two papers
• Cementing/zonal isolation, two papers
• Well control and blowouts, one paper
• Drilling operations, one paper
• Inflow-control devices, two papers
• Deepwater completions, one paper
• Tubulars, five papers

Carbon Capture and Storage

Carbon capture and storage (CCS) aims to reduce the amount of carbon dioxide in our atmosphere. Our first two papers examine the sealing ability of cemented wellbore sections to contain carbon dioxide injected into underground storage. The last issue of SPE Drilling & Completion (June 2011) also included a paper on CCS, so this is clearly a hot topic.

Leakage through new or existing wellbores is considered a major risk for carbon dioxide geological storage. Long-term effective containment is required; but, reliable data about long-term containment of CO₂ is almost nonexistent. The authors of our first paper, Quantifying the Risk of CO₂ Leakage Through Wellbores, used steam and methane injection wells as analogs to assess failure rates and consequences for cemented wellbores in CO₂ wells. Statistical data about occurrence of leaks and their consequences are analyzed to determine the risk profile of CO₂ leaks. A smaller sample of data about leak rates is also analyzed. Rates and consequences are then compared to try to assess the order of magnitude of major and catastrophic leaks. The paper concludes that cemented wellbores appear very effective at controlling leak rates and they will likely be as effective with CO₂ as they currently are with the steam and methane analog wells.

Our second paper also examines long-term sealing ability of cemented section in wellbores penetrating CO₂-storage reservoirs. A key concern is that microfractures inside wellbore cement or microannuluses are possible pathways for CO₂ leakage. The Effect of CO₂-Saturated Brine on the Conductivity of Wellbore-Cement Fractures presents an experimental study that investigates the changes inside the cement internal structure when exposed to acidic brine through an artificial fracture. Computed tomography scans and mercury intrusion porosimetry tests were conducted to assess changes in pore-size distribution. Environmental scanning electron microsopy was used to further investigate the nature of altered zones within the cement at a much finer scale. The impact of CO₂-rich brine on well cements under dynamic conditions appears to have dual effects on porosity of cement matrix. Low-pressure experiments showed porosity reduction for small pore sizes, while high-pressure experiments appear to cause increased porosity for large size pores. The authors conclude that, in terms of the behavior of wellbore cements under CCS conditions, it is possible that cements will undergo both dissolution and precipitation of new minerals. Further work is ongoing to quantify the change in permeability of cement with longer-term acidic brine exposure.

Cementing and Zonal Isolation

Dynamic Aspects Governing Cement-Plug Placement in Deepwater Wells reports a parametric study based on computational fluid dynamics to determine the influence of rheological properties of fluids (drilling fluid, spacers, and cement slurries), string rotation, and flow rates (including free-fall effects) on the quality of cement plugs. Guidelines and recommended procedures are provided for displacing cement plugs in vertical, inclined, and horizontal offshore wells. Fluid conditioning, spacer design, and pumping schedule procedures are highlighted.

In recent years, exploration activities in Kuwait have focused on Jurassic, Triassic, and Permian formations at depths between 15,500 and 20,000 ft. Cementing operations have presented major challenges because of high-pressure/high-temperature (HPHT) conditions, large casing sizes, oil-based mud, the presence of H2S/CO2, and narrow pore/fracture pressure window. Since 2003, work has been carried out to employ changes to technologies being developed in HPHT wells around the globe, especially in the North Sea. The result was a notable improvement in cementing performance. Ongoing Development of Cementing Practices and Technologies for Kuwait Oil Company’s Deep High-Pressure/High-Temperature Exploration and Gas Wells: Case History examines application of these technologies, materials, and practices over an 8-year period. This paper breaks down the many design elements of extremely challenging cementing operations. This solid case history provides excellent details comparing early and recent casing and cementing programs.

Well Control and Blowouts

Rotating control devices (RCDs) are used to provide a closed circulating system. Conventional wisdom suggests that drilling with RCDs improves kick detection and, thus, that fewer blowouts should occur when this equipment and related practices are deployed. Is conventional wisdom correct in this case? Yes, says The Impact of Rotating Control Devices on the Incidence of Blowouts: A Case Study for Onshore Texas, USA as it finds consistent statistical evidence that the use of RCDs decreases the incidence of blowouts using a sample of wells from onshore Texas from 2001 to 2007. Interestingly--perhaps even surprisingly--the paper concludes there is no consistent evidence to suggest that oil wells have more or fewer blowouts than gas wells. (It is more difficult to provide gas-tight casing connections than it is to provide oil-tight connections. Therefore, conventional wisdom might have said there should be more gaswell blowouts than oilwell blowouts.)

Drilling Operations

Traditional plug and abandonment (P&A) of exploration wells is accomplished by setting a series of cement plugs and mechanical retainer systems to isolate zones from each other and from surface. Permanent Abandonment of a North Sea Well Using Unconsolidated Well-Plugging Material describes a North Sea P&A field case study using an alternative method. An unconsolidated plugging material with high solids concentration was used to provide a gas-tight barrier. The authors claim the method avoids problems with well integrity that might be caused by cement shrinkage or fracture. The method requires a solid foundation; it cannot be placed on top of a liquid. The material is also not suitable as a foundation for a kick-off plug or behind structural (weight-/load-bearing) because of its relatively low shear strength. The paper shows how the fast and efficient placement of the plug contributed to overall cost reduction. It also explains how the well-barrier element complies with requirements in both the Norwegian and UK sectors of the North Sea. Operational procedures are presented.

Inflow-Control Devices

Inflow-control devices (ICDs) are completion hardware designed to distribute flow evenly in the reservoir. With a more-evenly distributed flow profile, production is less likely to suffer problems related to water or gas coning, sand production, and other drawdown-related issues. Understanding the Roles of the Inflow-Control Devices in Optimizing Horizontal-Well Performance investigates when and how ICDs should be used. An integrated analysis method of inflow (reservoir) and outflow (wellbore) is used to generate the flow profile of a horizontal well. Two conditions that result in production problems--wellbore pressure drop and reservoir heterogeneity--are addressed. Examples illustrate key points. The paper concludes that three production problems can be corrected by proper design and use of ICDs--the heel-toe problem, heterogeneous permeability distribution, and thin oil formation.

Our second paper on inflow control also addresses nonequalized production influx along a horizontal well. Multinode Intelligent-Well Technology for Active Inflow Control in Horizontal Wells describes a new technology to equalize production influx and delay water breakthrough more effectively than conventional, passive ICDs (as described in the preceding paper). The new system provides full electric remote actuation of downhole flow control for multiple valves with a single control line. This paper compares production and water-saturation profiles using the new technology to conventional ICDs in a horizontal-well simulation. The system is still under development; and, as the authors conclude, field data are required to prove the concept for production optimization and better reservoir management.

Deepwater Completions

Planning and Execution of Highly Overbalanced Completions From a Floating Rig: The Ursa-Princess Waterflood Project is a compelling story of a deepwater reservoir that has been on production since 1999 and is now undergoing a waterflood to increase and stabilize reservoir pressure and improve sweep efficiency. As more deepwater reservoirs approach depletion, specialized tools and procedures will be required to continue to deliver safe and effective sandface completions from floating rigs. This paper details many of these considerations and summarizes the execution and results from the main reservoir in the Mars-Ursa basin in the Gulf of Mexico. It is a must-read for anyone involved with or interested in deepwater fields.

Tubulars

We wrap up this issue with five papers related to tubulars. The first paper provides lessons learned from the past 20 years of successful application of torque-position makeup technology. Whether you are an expert in connections or someone who wants to know what LTC, STC, and BTC mean, you will benefit from reading Continuing Application of Torque-Position Assembly Technology for API Connections. This paper is an easy read that clearly details a critical and sometimes overlooked aspect of well construction.

Solid expandable liner systems were introduced approximately 15 years ago. My first exposure to expandables occurred at an SPE forum around 1995 when a video of the process was shown (yes, we used video in the 20th Century!). I recall thinking to myself "no, no, no" because intentionally inducing plastic deformation into a structural member conflicted with all my mechanical engineering training. Obviously, I was wrong because expandable systems were here to stay. Today, expandables provide viable options for dealing with major drilling hazards such as massive lost circulation or depleted zones. Major Advancement in Expandable Connection Performance, Enabling Reliable Gastight Expandable Connections asserts that, despite the progress, connection performance remains a problem. This paper details new cone-expansion technology that the authors claim eliminates the majority of damage to connections when expanded with traditional cones. Finite-element analyses and physical testing verification are provided to show how the new technology leaves connections with minimal visible damage to threads and metal seals after expansion. The paper concludes by stating developments of advanced connection designs are underway to provide enhanced pressure sealing and mechanical performance during and after expansion.

No standard procedure has been adopted by the industry to qualify casing connections for high temperatures up to 350°C. New Standard for Evaluating Casing Connections for Thermal-Well Applications introduces a new protocol for evaluating casing connections for thermal applications. The protocol, which was developed jointly by several operators and connection manufacturers, employs both analytical and experimental procedures. Adoption and use of the new protocol is expected to increase reliability and reduce failures of casing strings in thermal wells.

Our last two papers are courtesy of the same lead author. Dr. Rob Mitchell pulls off the rare double by publishing two papers in the same journal issue (and not a two-part series). His first paper points out that design calculations for casing and tubing forces and displacements are traditionally performed assuming the fluids are static. Obviously, this could be a significantly limiting assumption because casing must also withstand flowing fluid forces. Casing Design With Flowing Fluids adds the effects of fluid dynamics to the pipe equilibrium problem. The general equations for balance of fluid momentum are combined with the equilibrium equation for pipe. The effective forces emerge as a natural combination of pipe force and fluid-force terms. This mathematical tour de force is power packed and definitely worth a read for readers responsible for casing or tubing design.

Our final paper challenges conventional wisdom about how pipe buckles. The accepted paradigm has existed for more than 30 years, which is that buckling occurs first into a sinusoid and then into a helix. Torque and drag software programs calculate the onset of these buckling limits as well as the additional side force caused by the helix that leads to a condition known as lockup, which means that the pipe cannot be moved deeper into a wellbore. Lateral Buckling--The Key to Lockup analyzes the field data presented in an important paper (SPE-115930-PA) that was published in the December 2009 issue of SPE Drilling & Completion. In this prior paper, high-quality field data were obtained in a 2020-m research well known as Ullrigg U2. Readers may recall this paper concluded that current industry-standard calculations of the onset of sinusoidal and helical buckling did not match well with these field data. (Subscribers of SPE Drilling & Completion can download this paper from online archives.) The results of the new analysis show that connectors appeared to have primary importance in the buckling behavior of drillpipe. More important, this paper concludes that lateral buckling was the primary mode of behavior in these tests, not helical buckling. Neither of these results was expected. The authors state that conventional buckling models will require significant revision to account for these effects. Only time will tell, but this paper could represent a major transformation in buckling analysis.

That wraps up this issue. On behalf of your entire Editorial Review Committee, thank you for your continued support of SPE Drilling & Completion.

Curtis Cheatham
cheatham@spemail.org