As you might know, Executive and Associate Editor terms usually last “from ATCE to ATCE.” Therefore, in this December issue, cordial thanks are due to our outgoing Associate Editors (formerly: Review Chair) Richard Jachnik (Applied Fluid Systems Ltd, Aberdeen/retired) and Eric van Oort (The University of Texas at Austin), who dedicated their impressive expertise, experience, energy, and time over the last years to identify topics of interest and to improve these papers into quality articles for SPEDC!
At the same time, I have the pleasure to welcome two new members to our Editorial Review Committee, Bernt Aadnøy (University of Stavanger) and Vassilios Kelessidis (Texas A&M University at Qatar), who kindly agreed to lend their support as Associate Editors. As before, a short overview about the industry experts comprising the Committee will follow in the next (March) issue of SPEDC, when we also honor the crucial input of all our Technical Editors.
For those of you interested, some journal performance statistics are shared below, covering the period from July 2015 to June 2016 (period 2014/15).
Unfortunately (well, at least for me), this time we do not have any directly completion-related papers. Therefore, I take this occasion to encourage all of you to think about which of your (conference) papers could be a good candidate for SPEDC submission. Of course, we cannot promise to publish everything, but will do our best to provide you with a thorough and fair peer review of your manuscript.
And now on to our articles, which we hope support you in achieving your targets in the challenging environment we are currently in.
The first paper in this issue of SPEDC is about automated kick detection, a feature that is even more important to the safety of any drilling operation run during periods without circulation (i.e., connection make-up). In the paper Next-Generation Kick Detection During Connections: Influx Detection at Pumps Stop (IDAPS) Software, the authors start by explaining the reasons for software development (transient nature of flow when rig pumps are shut-down or ramped-up); discuss development steps, including functional requirements such as performance metrics, prototype testing, and incorporation of real-time operations center (RTOC) trials’ user feed-back; and describe the input data and how they are processed. Having tested program performance with a historical data set of 1,300 pumps-off events, it was rolled-out. Two examples of actual RTOC interventions triggered by IDAPS and future-development plans are shared, too. The authors show that the software is able to detect an influx in 100% of the cases, can confirm an influx in less than 180 seconds (on average), and has a false-alarm rate of only 0.5%. An approach potentially worth considering to further improve operational safety also for your crews and assets?
If your wells are targeting presalt (or subsalt) formations, our next article is especially for you because it describes the modeling of salt creep and its implications for casing (and completion) design. 3D Geomechanical Modeling of Salt-Creep Behavior on Wellbore Casing for Presalt Reservoirs provides an introduction to existing geomechanical salt models, explains the response of salt (in its different variations) subjected to stress, presents the modeling approach selected by the authors (drilling, transition, and production phases), and discusses the results obtained, with special consideration of the effects of casing eccentricity. The authors conclude that a 2D plane-strain model would underestimate salt mobility and, therefore, a 3D model should be used. If the internal casing pressure is less than formation stress, the von Mises stress in the casing will increase over time, but such a situation could be mitigated by catering for respective annular pressure management. The importance of good casing centralization before cementing is also reminded because it helps to reduce any bearing stress (nonuniform loading) on a casing string, hence collapse risk. Perhaps worth a discussion with the geomechanics specialist you trust?
With the following paper, we offer a comprehensive overview of how to analyze the load bearing capacity of conductors and surface casings. Having performed wellhead-growth calculations myself, I highly recommend reading, because it does not only provide a welcome “refresher” for the (more) initiated, but is also a very good introduction for all colleagues without (much) prior exposure to this trade.
In Structural-Casing/Soil Interaction Effects on Wellhead Motion, after a literature overview, the authors show how the pull-out capacity of a structural casing can be assessed, offer an explanation of the “ratcheting” phenomenon (irrecoverable, hysteretic length changes), and present an example calculation for a fixed platform well. In the appendices, the formulas needed to assess “axial pull on a buried hollow cylinder” and “length change of a buried cylinder” are provided. In their concluding remarks, the authors state that “it is difficult to rely on a single method or procedure” because of potentially irrecoverable length changes and the multitude of wellhead configurations or mudline suspension systems installed. Nevertheless, I think that you will find the presented work flow helpful, for example, the next time you are approached by your friendly pipeline engineer for tolerances.
For all colleagues keen to extend the run life of polycrystalline-diamond-compact (PDC) bits in formations where stick/slip is a common occurrence, reading the next article is certainly beneficial, because it describes an advancement of the (existing) depth-of-cut (DOC) control technology. In paper A Step Change in Drill-Bit Technology With Self-Adjusting Polycrystalline-Diamond-Compact Bits, the authors present the development of a self-adjusting DOC control cartridge mechanism, its operating principle (passive hydromechanical response to dynamic events), laboratory testing (cartridge and bit prototype), and actual field tests conducted in a research well onshore USA, where the new bit’s behavior was compared to a standard PDC bit and one with fixed DOC control (all in 8 ¾ in. size). The results show that a bit with self-adjusting DOC control has the potential to allow higher revolutions per minute (rev/min) at increased weight-on-bit without indications of stick/slip behavior in the two formations drilled (sandstone and dolomite). This could reduce the risk of vibration related failures and result in higher rate of penetration at the same rev/min, hence less mechanical specific energy required. Perhaps a bit design to be considered for your drilling operations?
Our next paper presents a solution to the challenge of placing (9 5/8 in.) casing shoes at exactly the right depth—not too shallow to avoid exposing reactive shale layers to subsequent completion operations, and not too deep to stay still above a highly permeable gas reservoir at initial pressure. Geo-Stopping With Deep-Directional-Resistivity Logging-While-Drilling: A New Method for Wellbore Placement With Below-the-Bit Resistivity Mapping explains the safety (well control) and well design drivers for using a deep directional resistivity (DDR) logging-while-drilling (LWD) tool when drilling these inclined big-bore subsea gas wells offshore Australia, the measurement principle and logic of this LWD geo-steering tool, and how it was adapted to look-ahead of the bit in nonhorizontal wells. Examples of tool performance in different geological situations (resistivity contrast and pore fill) are included together with a comparison to “classic” resistivity logs acquired later on. The authors share that in all seven wells, the 12 ¼-in. hole section total depth could be called within 3 m (approximately 10 ft) of the intended target zone, and they also discuss the limitations of the DDR system used (i.e., approximately 38° inclination for the detection of boundaries 3 m vertically below the bit). In my view, this is a very good example of a situation in which existing tools have been adapted to new needs, allowing the safe development of offshore reserves.
If you are interested in getting more out of directional survey data and improving well placement accuracy, the next article is certainly recommended. In paper New Instrument Performance Models for Combined Wellbore Surveys: A Move Toward Optimal Use of Survey Information, the authors describe how error models for individual survey tools are specified (instrument performance model, IPM), and, together with the trajectory data, are used as input into standard error-model software packages. If overlapping surveys are available, often only the most accurate one is used to represent the well trajectory, thereby discarding any surveys with larger uncertainty. Here, the authors propose to use all available data for improved quality control, explain how an averaged IPM file could be constructed, and present three example cases. It is concluded that the method works for any combination of surveying tools and contrast of accuracy and agrees well with results obtained by more rigorous (and more time-consuming) uncertainty calculations. Limitations such as highly curved trajectories (DLS) or the validity of the averaged IPM file (only to be used for the hole section and survey tools for which it was developed) are also discussed. An approach, which could help to get the most out of your (already existing) survey data.
Achieving a good seal from cementing is the objective of most jobs pumped, but temperature and pressure variations during the life of a well can put the integrity of the cement sheath at risk. To foster understanding of the potential failure mechanisms, our next paper presents a laboratory setup for the assessment of cement behavior under critical conditions. Experimental Laboratory Setup for Visualization and Quantification of Cement-Sheath Integrity starts with a literature review of studies and experiments performed to understand cement failure and sealing capability, describes the development of a test cell (application of pressure and temperature, computed tomography scanning for visualization), the required sample preparation (casing, rock, and cement), and presents some actual tests conducted with different casing surfaces (mill varnish, sand blasted, with oil-based mud film), and rock types (sandstone, shale). After sharing the test results, advantages and limitations of the developed test setup are discussed in detail. And you might take away some ideas on how actual subsurface environments could be scaled down and replicated for experimental investigations.
That’s it for our last issue in 2016. On behalf of the entire Editorial Review Committee, I thank you for your continued support of SPE Drilling & Completion.