Since the earliest fracturing treatments over 50 years ago, many different materials have been used including sand, glass beads, walnut hulls, and metal shot. Today's commonly used proppants include various sands, resin-coated sands, intermediate strength ceramics, and sintered bauxite, each employed for their ability to cost effectively withstand the respective reservoir closure stress environment. As the relative strength of the various materials increases, so too have the respective particle densities, ranging from 2.65 g/cc for sands to 3.4 g/cc for the sintered bauxite. Unfortunately, increasing particle density leads directly to increasing degree of difficulty with proppant transport and a reduced propped fracture volume for equal amounts of the respective proppant, reducing fracture conductivity. Intuitively, one expects a lesser density proppant would be easier to transport, allowing for reduced demands on the fracturing fluids, and if it had sufficient strength, would provide increased width, hence, enhanced fracture conductivity. Previous efforts undertaken to employ lower density materials as proppant have generally resulted in failure due to insufficient strength to maintain fracture conductivity at even the lowest of closure stresses (1,000 psi). Recent research on material properties has at last led to the development of an ultra-lightweight material with particle strength more than sufficient for most hydraulic fracturing applications. The current ultra-lightweight proppants have apparent specific gravity's of 1.25 and 1.75 g/cc. Laboratory tests will demonstrate exceptional fracture conductivity at stresses to 8,000 psi. This paper will present data illustrating the performance of the new ultra-lightweight proppant over a broad range of conditions and a discussion of relative performance in field applications. Introduction Ultra-lightweight proppants have been a subject of research efforts for at least a decade. Generally speaking, the stronger a proppant, the greater the density. As density increases, so too does the difficulty of placing that particle evenly throughout the created fracture geometry. Excessive settling can often lead to bridging of the proppant in the formation before the desired stimulation is achieved. The lower particle density reduces the fluid velocity required to maintain proppant transport within the fracture, which, in turn, provides for a greater amount of the created fracture area to be propped. Alternatively, reduced density proppants could be employed to reduce fracturing fluid complexity and minimize proppant pack damage. Two different avenues of ULW particle development research pursued in this area are presented. The first is a porous ceramic that uses novel resin technology to coat the outside of the particle without invading the porosity to effectively encapsulate the air within the porosity of the particle. Encapsulation of the air provides preservation of the ultra-lightweight character of the particles once placed in the transport fluid. Additionally, the resin coating significantly increases the strength and crush resistance of the ultra-lightweight ceramic particle. In the case of natural sands the resin coat protects the particle from crushing, helps resist embedment, and prevents the liberation of fines. The second avenue of research was directed towards an even lighter particle which may be described as a resin-impregnated and then, coated, cellulosic particle. The cellulosic substrate is sized, ground walnut hull. The low specific gravity of this particle allows near neutrally buoyancy behavior in flowing streams of slickwater type fluid. The application benefits of the ULW proppant are further enhanced beyond those discussed above. Resin impregnation and coating provide significantly enhanced strength beyond that afforded by the unaltered walnut hulls alone. Statement of Theory and Definitions The ULW-1.75 is a porous ceramic particle with the roundness and sphericity common to ceramic proppants. The porosity averages 50%, yielding a bulk density of 1.10 to 1.15g/cm3. Resin chemistry and processing technology have been developed to coat the particles, protecting the porosity from fluid invasion. If the resin coating or transport fluids were to significantly penetrate the porosity of the particle, the density increases accordingly, and the particle no longer has the same lightweight properties. The resin coat also adds strength and substantially enhances the proppant pack permeability at elevated stress. A comparison of the permeability versus closure stress of 1 lb/sqft of ULW-1.75 compared to Econoprop and Ottawa sand is shown in Figure 1.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractProppant flowback within deep hot wells and/or highly productive wells is a major problem in the oil and gas industry. Under these extreme conditions, many of the current products and processes to control flowback often fail. As such, improved or alternative technology and procedures are constantly being sought. One such technology is the development of deformable proppants.Material and structural improvement to a deformable proppant has allowed laboratory test conditions to be extended to higher temperature, closure stress and flowrate. As a result of this fine tuning, exceptional proppant flowback control has been obtained. Testing of this new deformable proppant, blended with typical fracturing proppant, has shown 50 fold increases in flowrate and 100 fold increases in pressure drop are attainable without pack failure, while still maintaining fracture conductivity.Furthermore, this deformable proppant has been applied in wells where current technology would either fail or have serious drawbacks. In two primarily gas producing reservoirs, the addition of this deformable proppant to proppant packs placed during fracturing treatments, has been observed to very effectively control proppant flowback under conditions of high bottom hole temperature, high fracture closure stress and high production regimes. In order to facilitate field application, new addition and monitoring procedures were developed to accomplish these successful fracturing operations. The developmental testing, successful application and well performance all indicates significant improvement in proppant pack integrity.

Enzymes represent an attractive alternative to oxidative chemical breakers for several reasons. They are polymer specific, environmentally friendly, easy to handle, miscible, do not damage equipment and they are naturally regenerating catalytic breakers. Enzymes have been used with great success for many years as breakers in fracturing applications.However, traditional enzyme breakers derived from mesophilic sources have a tendency to unfold from their functional threedimensional conformation into an inactive form under high temperatures. Thermal unfolding of enzymes proceeds via a dynamic equilibrium between active and inactive states, which reduces the enzyme activity, prior to an irreversible unfolding step as the temperature increases.To maximize enzyme functionality, a new generation of polymer-specific, thermostable enzyme was developed.The gene coding for the new enzyme was obtained and codon optimized for production in a commercially available expression system. Additional genetic enhancements were made to increase the yield and stability of the enzyme and further lower production costs.

Background/Objectives To report the incidence, microbiological profile and in-vitro antimicrobial susceptibilities of microbial keratitis (MK) in the East of England (EoE) over a 6-year period. Subjects/Methods A retrospective study of patients diagnosed with MK who underwent corneal scraping at participating trusts, within the EoE, between 01/01/2015–01/07/2020. Analysis was performed on MK isolate profiles, in-vitro anti-microbial sensitivities and trends over time. Results The mean incidence of IK, in the EoE, was estimated at 6.96 per 100 000 population/year. 1071 corneal scrapes were analysed, 460 were culture positive (42.95%) of which 87.2% were bacteria (50.3% gram-positive and 49.7% gram-negative), 2.4% polymicrobial, 9.3% fungi and 1.1% acanthamoeba. The most common organisms were pseudomonas spp (29.57%). There was a non-statistically significant trend (NST) in increasing incidence of pseudomonas spp, staph aureus and serratia ( p = 0.719, p = 0.615, and p = 0.099 respectively) and a declining NST in Fungi ( p = 0.058). Susceptibilities in-vitro to, penicillin classes, fluoroquinolone and aminoglycosides were 76.7% and 89.4%, 79.2% and 97.2% and 95.4 and 96.1% to gram-positive and gram-negative bacteria respectively. Gram-negative organisms were increasingly resistant to cephalosporins with a 19.2% reduction in sensitivity over time. ( p = 0.011). Ceftriaxone showed the greatest decrease in sensitivity of 41.67% ( p = 0.006). Conclusion In the EoE, MK is relatively prevalent though likely underestimated. Profiles are similar to other UK regions with the exception of a higher fungal and lower acanthamoeba incidence. Common first and second-line antimicrobial selection provides, on the whole, good coverage. Nevertheless, anti-microbial resistance, to cephalosporins, was observed so selection should be carefully considered when treating MK empirically.

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