Executive Summary

Welcome to the August issue of SPE Production & Operations. We have a real treat with this issue. In order 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. You will notice that I have deliberately included a broad selection of chemistry papers in this issue. I felt that this expanded issue was a great opportunity to showcase the broad application of chemistry in our industry. I hope that you agree!

I mentioned above that submissions to the journal are up. However, the quality of the papers is also higher, leading to an increased acceptance rate. Thank you. It is you, the users of the journal, the readers who are also authors, that make or break a journal and you are definitely making this one!

The first set of papers in this issue discusses various production technologies, starting with a discussion of sand deposition (Investigation of Critical Sand-Deposition Velocity in Horizontal Gas/Liquid Stratified Flow). Transport of sand in multiphase pipelines occurs as sand is produced and comingled with crude oil. Stationary sand beds are formed at the pipe bottom when the flow velocity is lower than the critical sand-deposition velocity. These sand beds then reduce production and affect the integrity of the pipe system, owing to pipeline plugging and erosion/corrosion. Therefore, the production system must be designed to operate at a velocity where sand particles are transported along the pipe and not deposited. For this reason, it is crucial to be able to predict the critical sand-deposition velocity. This paper describes experiments to study sand deposition and theoretical work based upon the experiments that are used to develop predictive correlations for the sand-deposition velocity.
   Balanced Reverse-Cleanout Operation: Removing Large and Heavy Particles From a Geothermal Well presents an approach to optimizing the cleanout efficiency of geothermal wells on the basis of field learnings from cleanout operations performed on a well in Germany.
  Next, we sneak in a paper that deals with well fracturing (Horizontal-Well Fracturing by Use of Coiled Tubing in the Belridge Diatomite: A Case History). This paper describes the use of coiled tubing to perform a multistage horizontal-well stimulation, a much more technically challenging activity compared with vertical well stimulation.
  Finally, in our discussion of production technology, Improved Tight Oil Productivity Through Integrated Technology Deployment on a Multipad Horizontal Well Trial in Central China describes a novel completion approach in the Ordos Basin that relies on the integration of several technologies.
We move on to three papers focused on artificial-lift technology. Numerical Study on Electrical-Submersible-Pump Two-Phase Performance and Bubble-Size Modeling proposes a novel, indirect approach to obtaining the representative bubble sizes inside a rotating electrical-submersible-pump (ESP) impeller. This is achieved by matching numerical-simulation results with experimental performance curves. A 3D computational-fluid-dynamics model is then implemented on a three-stage ESP geometry to simulate the pump-pressure increment under various flow conditions.
   Application of Data Mining for Quick Root-Cause Identification and Automated Production Diagnostic of Gas Wells With Plunger Lift presents an application of the regression-tree technique as a root-cause identification and production diagnostic tool. Case studies for gas wells using the plunger-lift system are presented. 
  Finally, we have a paper that discusses gas effects in ESPs (Gas Effect in Electrical-Submersible-Pump-System Stage-by-Stage Analysis). This paper describes stage-by-stage calculations of the intake and discharge pressures, allowing the total dynamic head for each stage of the pump to be adjusted. This allows for better design of the pump stages.

Chemical technology comprises our next topic, starting with two papers that deal with sulfide scales. Combined sulfide/carbonate-scale formation in wells producing from reservoirs with high carbon dioxide (CO 2) and high hydrogen sulfide (H 2S) represents a serious threat to production efficiency and system integrity. Iron Sulfide Scale Management in High-H2S and -CO2 Carbonate Reservoirs discusses combining calculations from pressure/volume/temperature software with scale-prediction software to accurately account for CO 2 and H 2S partitioning so that accurate calculations of the concentration of iron in aqueous solution can be made. This allowed the root cause of pernicious iron sulfide scale in a Middle Eastern gas well to be diagnosed. 
  Staying with sufide scale, A Systematic Investigation of Factors Affecting the Formation of Zinc Sulfide (ZnS) discusses work that was undertaken to investigate systematically the factors that affect the formation of ZnS in an aqueous system. Experiments were performed at a series of temperatures from room temperature up to 90°C, at a range of initial pH values and in two brine systems. This provides valuable data for calibrating scale prediction software.
  We change focus slightly in the next paper by discussing matrix acid stimulation (The Effect of Evolved CO2 on Wormhole Propagation in Carbonate Acidizing). In carbonate reservoirs, acid is injected into the formation to dissolve carbonate rock and create highly permeable channels called wormholes. In this study, coreflood studies are conducted to examine the effects of evolved CO 2 on wormholing behavior, which allows the optimal acid-injection conditions in the field to be determined. 
  Scale management in deepwater fields is both difficult and economically challenging and the risk to production great. Preproduction-Deployed Scale-Inhibition Treatments in Deepwater West Africa describes the application of scale inhibitor during fracturing treatments, which allows inhibitor to be present before water breakthrough occurs. The paper goes into detail on how to select inhibitors and gives information on five field treatments. 
  Staying with mineral scale inhibition, precipitation squeezing is an established method for increasing scale-inhibitor lifetimes. Solubility and Inhibition Efficiency of Phosphonate Scale Inhibitor_Calcium_Magnesium Complexes for Application in Precipitation-Squeeze Treatment is a very detailed and systematic study of the precipitation and solubility of three different phosphonate-based scale inhibitors.
  We now move away from scale management, but stay with the related topic of water management, with the next three papers in this area. As the shale-gas-extraction industry grows, there is much speculation regarding the types, magnitudes, and fates of the various types of wastes generated. As part of a life-cycle-modeling study, Trends in Fluid-Waste Generation From the Hydraulic Fracture and Operation of Shale-Gas Wells in Pennsylvania From 2012 to 2014 attempts to project water, salt, and solid-waste generation over a period of time in the life of wells for fields in Pennsylvania. The information and learnings gathered are put into context and are applicable across all fields of this type.
  Staying with water management, Disproportionate Permeability Reduction of Water-Soluble Silicate Gelants: Importance of Formation Wettability discusses a gel-based approach to reservoir water management. Disproportionate permeability reduction (DPR) potentially provides field solutions to address high volumes of water production in noncommunicating layered reservoirs. The paper evaluates laboratory-scale DPR effectiveness at different formation-wettability conditions by use of an environmentally friendly, water-soluble, silicate gelant.
  The final paper of this edition— Efficient Removal of Enhanced-Oil-Recovery Polymer From Produced Water With Magnetic Nanoparticles and Regeneration/Reuse of Spent Particles—presents the novel use of nanoparticles in the cleanup of water produced during a polymer flood. The magnetic nanoparticles (MNPs) are positively charged, which allows them to attract the negatively charged polymer. Once neutralized, the MNPs aggregate, which greatly facilitates the removal of the MNPs from the brine by the application of a magnetic field. The MNPs are regenerated by pH adjustment.

Why don’t you check out the Production and Operations page on the SPE website ( http://www.spe.org/disciplines/po/)? This will keep you abreast of the latest developments in this area and allow you to register for both technical and professional development webinars that you might find useful. I have personally found that the layout of the website has improved and that it is much more easy to use.

Finally, I firmly believe that we are heading for a digital transformation in our industry. The digital oil field has made great strides in certain areas, such as real-time monitoring and centralized operating centers. However, the concept has not yet fulfilled its ultimate promise. What is that ultimate promise and how will we get there? Why don’t you submit a paper answering this? I’d love to read it!

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