Executive Summary

 

 

 

Dear readers,

First of all I would like to cordially thank our outgoing Executive Editor, Carl Thaemlitz, for his outstanding work for and dedication to this journal. It makes me realize how high the bar has been placed. Luckily, he has agreed to continue supporting us with his expertise as Associate Editor!   

While the Executive Editor provides a “face” to SPE Drilling & Completion, the lion’s share of the peer reviews is shouldered by our Associate Editors (AEs).

Therefore I would like to take the opportunity to recognize the team of industry experts currently serving as AEs, dedicating uncounted hours to manage all our peer reviews assuring only quality papers are published (only main areas of expertise listed):

 

·         Ramadan Ahmed Well Control, MPD & Underbalanced Drilling, Research

·         Mark Brinsden      Perforating, Completion Planning, Design & Installation, Interventions

·         Curtis Cheatham  Directional Drilling, Drillstring Dynamics, Drilling Equipment

·         Shilin Chen                            Bit Design and Optimization, Drillstring Dynamics, Bit Selection

·         Alexander Crabtree              MPD and Underbalanced Drilling, Downhole Tools & Equipment

·         Barkim Demirdal  Drilling Fluid Rheology, Heavy Oil, Shale Gas

·         Richard Jachnik   Cutting Transport, Drilling Fluid Rheology, Rock/Fluid Interactions

·         Simon James                         Cement, Remedial Cementing, Zonal Isolation

·         John Mason                           Completion Planning, Design & Installation, Intervention Operations

·         Stephane Menand Drillstring Design & Dynamics, Bit Selection & Performance

·         Kaibin Qiu                             Geomechanics, Wellbore Stability, Compaction & Subsidence

·         David Stiles                            Cement, Wellbore Integrity, Lost Circulation

·         Carl Thaemlitz      Fluid Chemistry, Drilling Fluids, Handling, Processing & Treatment

·         John Thorogood   Real-Time Operations, Drilling Automation, Directional Drilling

·         Claas van d. Zwaag              Completion Planning, Design & Installation, Sand Control, Impairment

·         Eric van Oort                         Drilling Fluids, Handling, Processing & Treatment, Research

·         “Joe” Yunxu Zhou               Drilling Design & Analysis, Hydraulics, Multiphase Flow

 

Together with our >150 Technical Editors (unfortunately too many to name them here individually), and the SPE staff behind the scenes—they are the “backbone” of this journal—SPEDC depends on these individuals’ readiness to voluntarily dedicate their time and energy despite a busy schedule (… and to face the occasional challenge from family or friends—well, at least I do).

Personally, I am convinced that (a) sound and thorough engineering is the right thing to do, because more often than expected the “devil is in the detail.” But admittedly, there is also another school of thought concerned about the dangers of (b) “over-engineering.” However, the disciples of this school can be at risk of forgetting their previously propagated “80/20-approach,” especially if it is finally found that the neglected one-fifth is destroying project value and now has to be addressed at the “last minute” most frequently by colleagues having advocated (a) earlier on.

Like many others, I also believe that—especially in times of low oil prices and reduced staff levels—we simply cannot afford to ignore potentially useful new technology or methods. And if, for example, the acquisition of additional input data at additional cost improves our understanding of the task at hand, and we finally can achieve “more with less,” it should be well worth considering.

With that in mind, now on to our articles, which are meant to provide you with some additional ideas intended to support your professional endeavors.

 

 

Completion

Sand-control selection remains a challenge in many oil (and gas) provinces around the world. There is a wealth of literature available describing case histories and laboratory tests, providing screen-sizing criteria and recommending certain sand-control techniques in certain circumstances. Therefore, nowadays most companies have developed their own, well-established sand-control guidelines. But, we are—in general—a quite conservative industry and often prefer adhering to procedures already found to be working. This is the very reason why I recommend reading A New Approach for Selecting Sand-Control Technique in Horizontal Openhole Completions. After a literature review, the article describes recent developments in the areas of sand-alone screens (SAS) and gravel packing (including alternate path packing) within the last decade. It continues by offering the authors’ approach toward selection of an appropriate sand-control technique for horizontal, openhole wells with a clear recommendation for SAS as the base case (although not always possible) and illustrates it with four examples. And perhaps you will find that at least a discussion of the previously established selection guidelines could be beneficial for some of your assets?

Our second article in this issue of SPEDC presents a case history from the unconventional Barnett shale play onshore the US. In Case Study: Completion-Design Optimization for Barnett Oil-Producing Area, it is described how additional data acquisition from logging, microseismic monitoring, and cores combined with a detailed fracture stimulation data analysis supported the construction of an integrated subsurface model. On the basis of this enhanced understanding of the subsurface situation, completion designs with improved access to the existing natural-fracture network could be identified, which resulted in increased recovery levels when compared to similar offset wells. Perhaps something worth replicating in your (unconventional) fields?

 

Drilling

Although routinely performed, the accurate description of a non-Newtonian drilling fluid’s rheological behavior by selection of an appropriate model can be difficult. It often requires compromises to be made by selecting the model with the least deviation to the fluid’s actual shear response (i.e., being able to match only a certain range but not all data measured). In A Generalized Rheological Model for Drilling Fluids With Cubic Splines, the authors present an alternative. On the basis of a purely mathematical approach of curve fitting, they were able to achieve a close match over the whole range of actually measured data. The proposed methodology was compared with the response of commonly used rheological models for non-Newtonian fluids (i.e., Bingham Plastic, Power Law, Herschel-Bulkley, Sisko) and validated with published experimental data. In hole sections with narrow “drilling windows,” a closer representation of the mud’s rheological behavior in the hydraulics model could improve pressure predictions, thereby reducing risk in achieving the well’s objectives.

The next article fits well with the previous one by covering another topic of high importance in wells with small “drilling margins” and/or where managed-pressure drilling is applied—the representative prediction of fracture pressure. The paper Probabilistic Assessment of the Temperature-Induced Effective Fracture Pressures presents a mathematical model accounting for mud compressibility, thixotropy, and transient wellbore temperature to estimate fracture pressure from formation-integrity and leak-off test data. To reflect that many of this model’s required input parameters have an uncertainty range, a probabilistic assessment of the estimated fracture pressure was also performed, and its application discussed in two example cases from a Gulf of Mexico well. The authors conclude that ignoring temperature effects will lead to erroneous fracture pressure estimates, because the local geomechanical stress distribution changes when formations are cooled down (as observed also in water injectors). To reduce prediction uncertainty it is therefore recommended to stop mud circulation 1 hour before any formation strength test is performed.

Cementing conductor and surface casings in deepwater, subsea wells up to the seabed are critical for the structural integrity of such wells. But these large diameter top holes of uncertain actual quality in soft formations (washouts) can make cement placement challenging. Therefore, cement is typically pumped until returns from circulation ports at the seabed are confirmed by use of remotely operated vehicles. In Learning From Field Measurements: Engineering Method To Improve Cement Returns in Riserless Deepwater Jobs the authors present a logging while drilling calliper log on the basis of resistivity measurements to understand the actual borehole quality and integrate it into the proposed workflow, including post-job calibration of the hydraulics model. The complete approach is illustrated in a detailed case history. In my view this is another good example of where additional data—if correctly interpreted—can improve engineering results and increase our “probability of success.”

It is important to control the heat generated from exothermic cement hydration reactions, especially in permafrost regions or across gas-hydrate zones. But limiting the temperature rise by conventional approaches can lead to reduced (early) strength development of the cement sheath. The article Use of Microencapsulated Phase-Change Materials To Regulate the Temperature of Oilwell Cement introduces a new, microencapsulated phase-change material (MPCM) regulating temperature by physical means (namely phase changes absorbing and releasing heat). Because MPCM is encapsulated in a solid polymer shell, chemical reactions with the cement slurry are prevented. The authors share the experiments performed and discuss the results of the five slurries tested. They show that an MPCM with a properly tuned melting point is able to reduce the temperature rise from cement hydration and could also contribute to increased cement ductility.

If concerned with shallow coalbed methane (CBM) wells, or in general interested in the principles of “making hole,” our final article is for you because it explains hydraulic calculations and tool-design aspects for radial jet drilling (RJD) with high-pressure water jets.

After a description of the RJD process, the paper Hydraulics Calculations and Field Application of Radial Jet Drilling presents the experiments performed to define system pressure loss, ejector (jet) force (to destroy the rock), and the combined forces counteracting rate of penetration (extending resistance). The models derived from these laboratory results were compared with field data from six laterals drilled in a CBM well onshore China and found to be in close agreement (<8% error). The presented calculations can be useful for troubleshooting (i.e., in case of jetting issues), bottomhole-assembly optimization, and well design (i.e., maximum lateral reach possible).

 

That’s it for this first issue in 2016. On behalf of the entire Editorial Review Committee, I thank you for your continued support of SPE Drilling & Completion.

Kind regards,

 

 

Christoph Zerbst

 

christoph.cz.zerbst@pdo.co.om