Welcome back to SPE Production & Operations. I hope this edition provides you with solid science and engineering about topics you care about so that you can make better recommendations and decisions regarding your wells and projects. If you are disappointed in some way with this quarter's peer-approved papers, please be sure to read the last paragraph of this summary.
This edition contains nine peer-approved technology papers for your review, including five papers covering a diverse range of well-stimulation topics. Proppant Diagenesis--Integrated Analyses Provide New Insights Into Origin, Occurrence, and Implications for Proppant Performance contains a message that some of us thought we would never hear. The message is that the authors investigated something that could hurt fracture conductivity (zeolite precipitation on the proppant). After a thorough investigation, they learned that it is NOT expected to be much of a problem! The second stimulation paper, Case Study of Unconventional Gas-Well Fracturing in Hungary, shows the strategies used for the first two fracturing treatments in a field where there was a wide range of uncertainty regarding formation permeability when the work was planned. In A New Correlation of Acid-Fracture Conductivity Subject to Closure Stress, the authors provide a new model they believe can close the gap between large-scale simulation and microscale experiments. Their model combines geostatistical formation characterization with rock dissolution predictions and can identify and account for channel features that small-scale experiments fail to see. Under the conditions investigated in HCl/Formic In-Situ-Gelled Acids as Diverting Agents for Carbonate Acidizing, the authors showed that including formic acid with gelled HCl reduced the effectiveness as a self-diverting acid system compared to the performance of gelled HCl without formic acid. The final stimulation paper, Analysis of Nitrogen Stimulation Technique in Shallow Coalbed-Methane Formations, describes work done at the request of the Alberta Energy Resources Conservation Board to help them regulate shallow coalbed-methane fracturing using nitrogen with the intent of the work to identify appropriate measures to ensure the protection for shallow fresh water resources. The authors were able to incorporate data from approximately 2,000 wells and 20,000 fracturing jobs to accomplish their task.
Next we have two papers about well performance. An Analytical Solution for Water Coning in Vertical Wells provides a simpler solution to the old problem of how to optimize water-free production from a vertical well with bottom water. The authors show that partial penetration of less than half the reservoir is often the best solution. In Tapered-Bean Steam Chokes Revisited, the authors show higher rate capacities with good rate control and acceptable pressure recovery from using 4-in.-long or even 3-in.-long bean chokes instead of the more common 6-in. length. They also show that the Thornhill-Craver equation can still be used to calculate the steam flow rate through these shorter chokes with acceptable accuracy.
We wrap up this edition with a paper about monitoring and optimizing well performance in a scaling environment and another paper about sand control using scale. In Application of Multirate Tests to Scale Management: Part 1--Interpretation of Produced-Water Analyses, the authors introduce the application of a new method that relies on water analyses and multirate production testing through a surface testing facility to determine zonal contributions from commingled wells. Part 2 will follow in our next edition. The final paper in this edition is an interesting look at a process to intentionally create scale to reduce or eliminate sanding in the targeted zone. The authors of Controlled Use of Downhole Calcium Carbonate Scaling for Sand Control: Laboratory and Field Results on Gullfaks describe a creative injection process using three chemicals, one of which slowly catalyzes the formation of calcium-carbonate scale in the interval where the treatment has been placed to strengthen the rock and reduce sand production.
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