Polyacrylamide-based friction reducers (FR's) - including viscosifying polyacrylamides, which are designed to decrease proppant settling by increasing molecular weight and/or active material in the FR - are used extensively in high-rate fracture stimulations. However, because polyacrylamides are difficult to break, there have been concerns about how these materials impact fracture conductivity and formation permeability. This study presents the effect of conventional and novel oxidative breakers over the viscosity and colloidal size distribution of the broken polymers. Breakers tested include conventional persulfates, perborates and patent pending peroxides, all of which generate free radicals to degrade partially hydrolyzed polyacrylamides (PHPAs). Breakers were tested at bottomhole temperatures encountered in the Permian, Bakken, Haynesville and Eagle Ford. Changes to PHPA viscosity were determined using vibrational viscometers. Size distributions and percentage of the broken colloidal PHPA were determined by dynamic light scattering. This method can measure sizes down to 0.6 nanometers, which is within the range of even the smallest pore-throat sizes in shales. Light scattering revealed surprising anomalies in breaker performance. When aged at temperatures typical of the Permian, each of the tested breakers at each of the varied concentrations caused similar levels of viscosity reduction but different size distributions. Some breakers had the unwanted effect of narrowing the colloidal size fractions to the lower end of the spectrum. At these small sizes, colloids are more likely to overlap with segments of the pore throat distribution in some shales, which could inhibit production. In addition, when the FR was aged at the higher temperatures encountered in the Bakken, Eagle Ford and Haynesville, some breakers were not able to uniformly break the PHPA. In these cases, FR's without breakers delivered superior performance. The results clearly demonstrate that breakers may not always have the desired effect of increasing the formation's permeability. In fact, depending on the type of breaker and the concentration, they can often have detrimental effects that ultimately hinder production.

No abstract

No abstract

Smaller shaped charges with a 34 to 43-mm, 18-to-21-gram Copper-Lead liner (Tungsten added for "Deep Penetrators"), engineered for 318 -in OD guns, targeting US Land shale, can produce, an average, a lateral entry of 0.36-inches. A larger diameter entry-hole (EHD), based on perforation design (limited entry vs. high perf. design) has several benefits: lowering of "Perforation Friction" (Pf), lowering of treatment pressures, larger flow across each perforation, fewer chances of a screen-out, uniform drainage, and engineered completions where larger EHD perforations can be placed at the "Toe" with decreasing EHD perforations towards the "Heel" to offset wellbore fluid friction, especially in 3-mile long lateral "Toe". Such was the motivation behind engineering a water reactive, degradable-liner from High-Entropy-Alloys (HEA), producing a significantly larger entry-hole and accompanying debris-free perf-tunnel from a smaller charge, without changing the liner geometry or size, such that it can be universally accommodated in smaller diameter API gun, for example with a 318-in OD. A step change in adding sensing and intelligence to a shaped charge, enabling remote monitoring of zonal performance through strategic deployment of the product, was envisioned for the very first time, adding smart nano-particulates as unique identifiers or tracers in the composite liner bulk. As these novel charges are fired, the thermally stable, doped, nanoparticle rare earth oxide (REO) tracers are carried by the jet and deposited in the perforation tunnel. Hypothesized was their control release during flowback, being conveyed back to the surface with production. These nanoparticle tracers can be identified when they pass through an in-line detector with a collimated light source of predetermined wavelengths, illuminating the tracers, emitting photons with a unique fingerprint, thus identifying the nanocrystal. The detector, comprising a remote computing system configured to store and relay information relating to these tracers is under development. This industry first is a paradigm shift in remote-monitoring, alerting any end user, anywhere in the world, of selected downhole event triggers, without running any device in the well. Never before envisioned innovation to identify non-productive zones, diverter effectiveness, water break out and much more can now be determined, effectively and economically. A five-well field trial of tracer shaped charges with degradable liners were undertaken in the Permian shale (US Land), shot in parallel to industry premium charges, every other stage for selected stages, for a comparative performance analysis. Generally observed were: Up to (a) 10% less time to design rate (b) lowering of pad volumes (ESG) (c) distinct reduction in perf-friction (d) Successful tracer conveyance via charges and returns with flowback fluids to surface. Given its superior performance, far exceeding initial field introduction metrics, tracer charges with degradable HEA liners are predicted to be a game changer in harnessing formations with high frac-gradient and tight rocks, including carbonates in Middle East and North Africa (MENA).

Chemical and oxidative biocides are designed to sanitize water by reducing aerobic and anaerobic bacterial populations in the fresh, brackish and reclaimed source waters. These biocides are used extensively in high-rate fracture stimulations to reduce formation damage, chemical degradation, biogenic H2S and microbial induced corrosion (MIC). Oxidative biocides work by removing electrons from the cell wall of aerobic and anaerobic bacteria. The same electron transfer mechanism can be detrimental to surface equipment. This study presents the impact of several oxidative biocides on the corrosion rate and pitting of different frac iron alloys and how those biocides effect the mechanical integrity of elastomer seals. It also presents different remediation methods to mitigate their oxidative effects. The oxidative biocides tested were Chlorine, Chlorine Dioxide and a Peracidic Acid blend. The corrosion rate of the iron alloys coupons was measured by weight loss analysis. This method can measure the rate of corrosion in pounds per square foot at time and was used to compare the impact of different residual oxidizers on the corrosion rate of the ground iron. Structural changes to the elastomers were detected visually. The results of the study showed that the corrosion rate varied depending on the alloy/residual oxidative biocide combination. Usually, Peracidic Acid blend or Chlorine had the highest corrosion rates across all alloys tested; depending on the oxidative biocide/alloy combination, the corrosion rate could vary by a factor of 2X over the nine-week timeframe. Elastomer testing over 6 weeks showed variability in the types of structural changes depending on the concentration and oxidative biocide tested. The lab and field testing included onsite monitoring of the corrosion rate, oxidation reduction potential (ORP), oxygen in solution and determination of the Langelier Saturation Index (LSI). The methodology has been effective in predicting iron failures related to the composition of the water and/or presence of oxidizers. Chemical solutions implemented to mitigate the surface iron failures included use of intermittent blends of water-soluble quaternary amines and surfactants. Since these remediation attempts have started, the replacement cost of frac iron has decreased from over 550K US$ per month, per frac spread to none, over a 3-month period.