Executive Summary

Welcome to the November issue of SPE Production & Operations. Sadly, this is my last summary as Executive Editor (EE) because, after 3 years in the role, I am handing over the reins to Frank Chang. Many of you will know Frank and hence will know that you are in good hands. It has been an honor to serve in this role. During my tenure, the industry has been hit by low oil prices and much change and turbulence. When I started as EE, oil was at ca. $120/bbl; now as I write, it is just over $60/bbl, having plumbed unprecedented depths in between. It has been a challenge to maintain a high-quality peer-review process during this time, as the industry has reinvented itself and slimmed down. However, thanks to you, the dedicated technical professionals in the industry, I hope that you agree that we rose to the challenge and have not just maintained but grown the quality of the journal.

As with the previous issue, to help clear the backlog of unassigned papers (a consequence of the increasing number of high-quality submissions to the journal), we have increased the paper count to 15. 

Hydraulic Fracturing
The first set of papers in this issue is devoted to one of our most popular topics: hydraulic fracturing. Our first paper, Laboratory Testing on Proppant Transport in Complex-Fracture Systems discusses injecting a low-viscosity sand-laden fluid at a high flow rate. Such a treatment has the capacity to form complex-fracture networks. The paper provides an experimental exploration of the parameters that control the fracturing process, together with simulation results. 
  Continuing the theme, our next paper is focused on improving fracture conductivity. A conventional proppant pack may lose up to 99% of its conductivity because of gel damage, fines migration, multiphase flow, and non-Darcy flow. Computational Fluid Dynamics Applied To Investigate Development of Highly Conductive Channels Within the Fracture Geometry describes the concept of pillar fracturing, which was developed to generate highly conductive paths for hydrocarbon to flow. Experimental results and numerical models of a new method to generate stable proppant pillars are described. 
  Next, we move onto a less familiar topic: coal stimulation. Applications of Geomechanics to Hydraulic Fracturing: Case Studies From Coal Stimulations describes examples from hydraulic-fracture stimulations of coals in a complex but well-characterized environment (Surat Basin, eastern Australia). The authors obtain reservoir-rock-related input parameters that are important to the design of hydraulic fractures and use these data to optimize fracture-treatment design.
  Flowback data from seven multifractured horizontal tight oil/gas wells in the Anadarko Basin is analyzed in Estimating Effective Fracture Pore Volume From Flowback Data and Evaluating Its Relationship to Design Parameters of Multistage-Fracture Completion. The data show two separate regions during the single-phase water production. Region 1 shows a dropping casing pressure, and Region 2 shows a flattening casing pressure. The paper investigates the flowback behavior of the two regions, and illustrates how flowback data can be interpreted to estimate effective fracture pore volume, and to investigate its relationship to completion-design parameters. 
  Our final paper in this section (Next-Generation Boron-Crosslinked Fracturing Fluids: Breaking the Lower Limits on Polymer Loadings) describes a novel boron crosslinked fracturing fluid. This chemistry paper provides a link to our next section on production chemistry.

Production Chemistry
We move on to five papers focused on production chemistry. Modeling of Geochemical Reactions Occurring In the Gyda Field Under Cold-Seawater Injection on the Basis of Produced-Water-Chemistry Data and Implications for Scale Management shows produced-brine-chemistry data from 16 wells in the Gyda field. The data are plotted and analyzed using general geological information and information from the reservoir description. A 1D reactive-transport model is then developed to identify the possible geochemical reactions occurring within the reservoir triggered by seawater injection. This is then extended with the inclusion of thermal modeling. 
  We move from inorganic scales to the organic type with A Pigging Model for Wax Removal in Pipes. Pigging is widely used in pipelines for wax removal. However, because of the complexity involved, pigging operations rely heavily on “rules-of-thumb.” This paper aims to overcome these problems and develop a quantitative pigging model for wax removal in pipelines. Like wax deposition, asphaltene precipitation is a common phenomenon in mature reservoirs that seriously impairs oil production. In high-temperature, fractured carbonate reservoirs, the situation becomes critical when asphaltene precipitates at reservoir conditions, blocking the production channels and starting a cycle of production decline in which additional pressure drop promotes further precipitation of the asphaltenes.
   Asphaltene-Prevention Work Flow Enhances Oil Production in High-Temperature Fractured Carbonate Reservoirs describes an integrated diagnosis work flow that includes the creation of asphaltene phase envelopes and the determination of asphaltene onset pressures for two mature fields in Mexico. This allows accurate determination of where the asphaltene deposition is occurring and the development of a preventative solution involving bullheading asphaltene inhibitor.
  Remaining with asphaltene control, Emerging Numerical-Modelling Technique To Evaluate Asphaltene-Inhibitor Efficiency During Entire Field Life describes the establishment of a robust asphaltene flow-assurance approach, again involving the use of asphaltene inhibitor to mitigate the risk of asphaltene precipitation in the production tubing. For this purpose, the best candidate was selected through the asphaltene dispersant testing. Furthermore, the inhibitor efficiency was evaluated by generating a numerical model. 
  The final paper in this section deals with methane-hydrates as a hydrocarbon source. The first offshore methane-hydrate production test was conducted in the Eastern Nankai Trough area of Japan in 2013, subjecting a gas-hydrates reservoir to large drawdowns by reducing bottomhole pressure, leading to in-situ dissociation of the gas hydrates. This pioneering test is described in Issues and Challenges with Controlling Large Drawdown in the First Offshore Methane-Hydrate Production Test. The test proved the feasibility of the depressurization method through demonstration of gas production from the reservoir. Approximately 119 500 std m 3 of gas was produced during a continuous flow period of 6 days.
 
Wells Technology
Our final section in this issue deals with a variety of production technologies. Successful 20-Well Stimulation Campaign in a Mature Oil Field in Myanmar discusses the challenges seen and the results obtained using hydraulic-fracture stimulation in a mature oilfield. Having snuck in this extra hydraulic-fracturing paper, we now move on to a very different topic: gas well deliquification.
  After gas wells are drilled and start producing, early production rates are high enough to carry any liquid produced to the surface. However, as the reservoir pressure declines, the gas-production rate also declines. Eventually, the gas well starts experiencing liquid loading, which impairs gas production. Field Trial of a Novel Self-Reciprocating Hydraulic Pump for Deliquification discusses a novel hydraulically powered, self-reciprocating valve pump (SRVP) that was piloted in a western Colorado gas well for deliquification operations. The objective was to pump liquids from a deep gas well and later retrieve and redeploy the SRVP without a workover rig. The paper describes the SRVP technology, areas of applicability, and pilot program, including the completion design, deployment/retrieval workovers, performance, teardowns, learnings, and future plans.
  We keep to the same topic with Improved Prediction of Liquid Loading in Gas Wells. This paper describes a new method, which is a modification of previous methods, for predicting liquid loading. The proposed method accounts for the effect of the diameter and inclination of the gas well. 
  We change tact now and discuss water injection. Water injection is commonly used to improve oil recoveries in depleting reservoirs. However, insufficient injectivity can result in water-injection projects being limited in injection rates, which can sometimes make them uneconomical. Implementing water-injection projects requires a multidisciplinary approach to optimize water-injection rates for reservoir-performance, cost, and well-design considerations. Accordingly, Optimizing Water-Injection Design in a Shallow Off-Shore Reservoir describes a multidisciplinary work flow that can be used to improve surface facility design. 
  Our final paper in this section, and indeed, this issue, is A Numerical Study on the Thermal Behavior of Wellbores. The thermal behavior of a deepwater well was simulated using an existing mathematical model in which a rigorous flow-pattern-based multiphase-flow method was used to predict the pressure drop of the hydrocarbon stream. The heat-transfer model relied on the energy equation applied to the hydrocarbon mixture and on a radial thermal-resistance network between the wellbore and the formation. Different annulus-convection and thermal-formation models were also evaluated.

In conclusion, I offer a big thank you to SPE for the opportunity to broaden my education by editing the journal and a heartfelt thanks to all the SPE staff and journal editors who have supported me during my tenure. Au revoir!

Ian Collins, SPE Prod & Oper Executive Editor;
BP Exploration