Many open-hole acid treatments are being conducted by pumping acid through jetting ports placed at the end of coiled tubing or drill pipe. The filter-cake on the bore-hole is broken by the jet; the acid-soluble material is dissolved, creating wormholes in the formation. This combination of two acting factors creates more stimulation beyond the jetting action area. Existing papers have mentioned the advantages of using jetting both for damage removal and as the preliminary stage before further acidizing. Many papers discuss theory and practical implementation of wormholing during acid jobs and the resulting injectivity enhancement, too. However, there is no complete research regarding jetting efficiency with regards to permeability restoration due to filter-cake disruption, and therefore, no data exists for efficient filter-cake removal by acid jetting just prior to wormholing. My project objective is to conduct experiments of acid jetting, defining the parameters that aid to restore injectivity. Based on the parameters obtained from the experiments, I developed a set of recommendations for acid jetting design and optimization.

Many open-hole acid treatments are being conducted by pumping acid through jetting ports placed at the end of coiled tubing or drill pipe. The filter-cake on the bore-hole is broken by the jet; the acid-soluble material is dissolved, creating wormholes in the formation. This combination of two acting factors creates more stimulation beyond the jetting action area. Existing papers have mentioned the advantages of using jetting both for damage removal and as the preliminary stage before further acidizing. Many papers discuss theory and practical implementation of wormholing during acid jobs and the resulting injectivity enhancement, too. However, there is no complete research regarding jetting efficiency with regards to permeability restoration due to filter-cake disruption, and therefore, no data exists for efficient filter-cake removal by acid jetting just prior to wormholing. My project objective is to conduct experiments of acid jetting, defining the parameters that aid to restore injectivity. Based on the parameters obtained from the experiments, I developed a set of recommendations for acid jetting design and optimization.

Formate-based mud has been used to drill deep gas wells in Saudi Arabia since 2004. This mud typically contains XC-polymer, starch, polyanionic cellulose, and a relatively small amount of calcium carbonate particles, and is used to drill a deep sandstone reservoir (310°F). Calcium carbonate particles are frequently used as weighting material to maintain the pressure that is required for well control and minimize the leak-off. Such solids become consolidated and trapped in the polymeric material and this makes the filter cake a strong permeability barrier. Various cleaning fluids were proposed to remove drilling mud filter cake; including: solid-free formate brine and formate brine doped with organic acids (acetic, formic, and citric acids), esters, and enzymes. The main objective of this research is to assess the effectiveness of these cleaning fluids in removing drilling mud filter cake. A dynamic high-pressure/high-temperature (HPHT) cell was used to determine characteristics of the drilling mud filter cake. Drilling mud and completion fluids were obtained from the field. Compatibility tests between potassium formate brine, cleaning fluids, and formation brine were performed at 300ºF and 200 psi using HPHT visual cells. Surface tensions of various cleaning fluids were also measured at high temperatures. The conventional method for cleaning the filter cake is by circulating solid-free formate brines at a high flow rate. This mechanical technique removes only the external drilling fluid damage. Citric acid at 10 wt%, formic acid, and lactic acid were found to be incompatible with formate brine at room temperature. However, these acids were compatible with formate brine at temperatures greater than 122°F. Only acetic acid was compatible with formate brine. A formula was developed that is compatible at room and reservoir temperature. This formula was effective in removing filter cake. A corrosion inhibitor was added to protect downhole tubulars. In general detail, this research will discuss the development of this formula and all tests that led to its development.

The main goal of drilling a horizontal well is to enhance productivity or injectory by placing a long distance drain-hole within the pay-zone. Poor drilling fluid design results in difficulties such as poor hole cleaning, excessive torque or drag, wellbore instability, stuck drill string, loss of circulation, subsurface pressure control, poor cement jobs, and difficulties associated with running electric logs and formation damage can result. Neither of the conventional chemical cleaning methods can overcome problems for filter-cake removal in long horizontal and maximum reservoir contact wells because of limitations such as the complex geometry of wells, non-uniform chemical distribution, low contact between cleaning fluids/filter cake, and high chemical reaction rate, especially at high temperatures. This study describes a novel self-destructing drilling fluid system. Filter cakes are formed from a formula of drilling fluid that have a mixture of solid acid precursor and particulate solid acid-reactive materials. Then in the presence of water, the solid acid precursor (polylactic acid) hydrolyzes and dissolves, generating acids that then dissolve the solid acid-reactive materials (calcite). It effectively stimulates the horizontal section right after drilling and eliminates acidizing, resulting in significant cost savings, and improves filter-cake removal, thus enhancing the performance of the treated wells. A series of experiments have been run in the lab to determine the efficiency of this new system. Properties of this drilling fluid are measured. Experiments on solid acid particle size showed that the best size-distribution of solid acid precursor and solid reactive material to make a self-destructing filter cake is fine particles of calcium carbonate used as weighting material with 150 microns polylactic acid as solid acid precursor. By comparison of the results of the experiments at different temperatures, 230 degrees F has been chosen as the best temperature for running experiments. The self-destructing drilling fluid systems need enough time for the solid acid to be hydrolyzed and therefore remove the filter cake. After 20 hours of contact with the water as the only cleaning solution, about 80 percent of the filter cake was removed. Calcite is found to be the dominant compound in the sample of remained filter cake, which was proved by x-ray diffraction tests. Secondary electron microscopy (SEM) results show the morphology of the remained filter cake sample and confirm the crystalline area of calcite.

The hydraulic fracturing treatment is an essential tight sand gas reservoir stimulation that employs viscous fluid to break the formation rock to create a fracture and transport the propping agent to support the fracture from naturally healing. Despite proven economic benefit, the hydraulic fracture fluid damages the producing formation and the propped fracture. To analyze the gel damage effect quantitatively, the filter cake thickness is used as a parameter that has not been measured before. This project was divided into two stages. The first stage built up a filter cake and measured the filter cake thickness by a laser profilometer. A correlation between leakoff volume and filter cake thickness was produced. The second stage eroded the filter cake by flowing original fracturing fluid through the core sample to study the fracturing fluid shear clean up effect on filter cake thickness. The filter cake was built up in the lab and the thickness was measured with different methods. The profilometer has been tested as an effective tool to measure the filter cake thickness. A correlation for crosslinked guar fracture fluid filter cake thickness was produced. An experiment setup used to shear erode the filter cake was built and tested. The results showed the filter cake was not eroded at 200 s-1 shear rate.

Filter Cake, which contains leachable nickel and vanadium above the criteria in the Alberta Waste Control Regulation, is produced at an oil sands facility operated by Nexen Inc. and is currently being disposed in a landfill. Bench scale and field tests were performed with stabilization/solidification (S/S) treatment reagents such as Portland cement, fly ash, elemental sulphur, and CETCO Oilfield Service’s proprietary reagents to assess their efficacy at reducing leachable metals in Filter Cake. The CETCO reagents were the most effective treatment for reducing leachable nickel and vanadium in Filter Cake. Treatments with Portland cement were successful in bench scale tests, but inconsistent in field tests. The inconsistent results obtained for Portland cement may have been due to interferences of the cement reactions from factors such as fine particulates. S/S treatments of Filter Cake present a viable waste management option. However, the associated reduced cost and environmental impacts were not substantial.

The ability of starch to impart functions including fluid-loss control, cuttings transport, and rheological characteristics to water-based drilling fluids has led to its widespread use in the oil industry. The filter cake deposited by these drilling fluids often employs sized solid particles and starch to inhibit fluid loss into the formation. This inherently causes damage to the formation by impairing the permeability and must be removed before production. An alpha-amylase enzyme treatment was found to provide an effective approach to degrading starch in filter cake. In this work, an alpha-amylase enzyme treatment was analyzed by determining the extent of degradation of starch in filter cake using the iodine test, identifying degradants using high performance liquid chromatography, spectrophotometrically monitoring the concentration of enzyme, and measuring the cleanup efficiency of the enzyme treatment using a static filter press apparatus. The alpha-amylase enzyme used in this study was found to have a molecular weight under 30,000. The activity of the alpha-amylase enzyme was found to be sensitive to pH and temperature. The alpha-amylase enzyme was found to denature at temperatures above 165 degrees F and reversibly deactivate at pH below 4. Optimal conditions for alpha-amylase activity were found to be 150 degrees F and pH 6.5. The enzyme treatment works by hydrolyzing the interior glycosidic bonds of amylose and amylopectin residues of starch, creating soluble poly- and oligosaccharides and glucose. The enzyme treatment did not dissolve the calcium carbonate sized solids and a 5 wt. % hydrochloric acid postflush was necessary. The cleanup efficiency of the enzyme at pH 6.5 and room temperature treatment in conjunction with the postflush in a static test was 73% at 10% v/v concentration. Degradants resulting from alpha-amylase were identified chromatographically. Enzyme concentration remained steady prior to and after treatment.

Doctor of Philosophy / Department of Grain Science and Industry / Subramanyam Bhadriraju / Filter cake and Triplex are powdered by-products of aluminum sulfate and soap factories, respectively. Studies were designed to determine elemental composition of these two powders and evaluate the efficacy against stored product insect species on concrete surfaces and commodities. Elemental composition of the powders was determined using conjugated scanning electron microscopy and Energy-dispersive X-ray spectroscopy. No heavy metals were found in both powders, and the dominant elements found were silicon and oxygen in the form of silicon dioxide. The efficacy of filter cake and Triplex against the maize weevil, Sitophilus zeamais Motschulsky; rice weevil, Sitophilus oryzae (Linnaeus); lesser grain borer, Rhyzopertha dominica Fabricius; red flour beetle, Tribolium castaneum (Herbst); saw-toothed grain beetle, Oryzaephilus surinamensis (Linnaeus); and Indian meal moth, Plodia interpunctella (Hübner), was determined using a range of concentrations and exposure times. On concrete surfaces ≥ 7.5 g/m² of filter cake produced more than 99% mortality of S. zeamais and S. oryzae adults within 12–24 h, whereas more than three times the concentration of filter cake was required to achieve similar mortality of both species in Triplex treatments. At 3 g/m² of filter cake, 99% mortality S. zeamais and S. oryzae adults was achieved within 22–27 h of exposure. The corresponding exposure time at 9 g/m² of Triplex was 39 h to achieve 99% mortality of both species. For both powders, lower concentrations and exposure times were required to achieve complete suppression of progeny production, percentage of insect damaged kernels, and percentage of grain weight loss compared to the concentrations and exposure times required for 00% mortality. Filter cake treated wheat at concentrations above 0.7 g/kg produced more than 99% mortality of S. zeamais and S. oryzae adults. Similarly, filter cake concentrations above 2 g/kg on wheat produced more than 99% mortality of R. dominica, T. castaneum, and O. surinamensis adults. However, on maize ≥ 3 g/kg of filter cake concentration was required to achieve similar mortality of R. dominica, T. castaneum, and O. surinamensis. Higher concentrations of Triplex were required to achieve similar mortalities of tested species on maize and wheat. Reduction in progeny production was greater when adults were exposed to higher concentrations than lower concentrations. Complete suppression of live larvae and adult emergence of P. interpunctella was achieved after exposure of eggs for 21 and 42 d to ≥ 2 g/kg of filter cake treated maize and to ≥ 0.5 g/kg of filter cake treated wheat. Similarly, complete suppression of live larvae and adult emergence was achieved when eggs were exposed to ≥ 6 g/kg of Triplex treated maize and to 3g/kg of Triplex treated wheat. In general, our study consistently showed that filter cake was more efficacious compared to Triplex against all tested species on both surfaces and commodities. Filter cake and Triplex should be recommended for protecting grain stored by smallholder farmers in Ethiopia to discourage farmers from using dangerous chemical insecticides. However, field studies should be done using both powders against stored product insects in smallholder farmers’ traditional storages structures in Ethiopia to determine concentrations that are practical under field conditions. The effective duration of protection offered by these powders should also be investigated.

Due to the widespread use of drilled shafts in state and federal highway bridges, strict regulation of the design and construction has been imposed by the respective agencies. However, documented cases of anomalies and/or poorly performing shafts continue to arise. To this end, this thesis investigates several aspects of drilled shaft construction that may affect the quality of the finished product. These areas include bentonite slurry properties and performance as well as reinforcement cage and concrete flow interactions. Recent research indicates tremie poured concrete does not flow as predicted. Instead of even rising, a differential between the height of concrete inside and outside the reinforcement cage has been observed. Compounding this problem is the fact that bentonite slurry used to support boreholes may settle suspended sand at the toe of the shaft or on the surface of rising concrete during long wait periods, affording the possibility of soil inclusions in the shaft. This thesis examines two methods of inquiry to quantify the behavior of concrete in a tremie pour drilled shaft and sand suspension behavior of bentonite slurry. Conclusions and recommendations are made to improve pertinent construction regulations to ensure quality of drilled shafts.

The sugarcane industry in Brazil produce large amounts of organic wastes including vinasse and filter cake which have been applied to agricultural soil in appreciable amounts over the past two decades. This study examines the chemical characteristics of vinasse and filter cake and their interaction with soil particles. The total concentration of heavy metals found in these residues were relatively small and considered environmentally safe for land application. About 22-100% of the total concentration of Cu, Fe, Mn, Ni, Pb and Zn in vinasse are in water soluble forms compared to only 0.3-17% in filter cake. Elevated amounts of sulfate, chloride and dissolved organic carbon (DOC) were found in the <0.22-[mu]m fraction of vinasse. Filter cake samples had high amounts of phosphate and neutral pH. Most of the 13C NMR spectra of the DOC fraction of vinasse comprised of O-alkyl and carboxyl carbons. The presence of carbohydrates and COOH/COO- was suggested by the FTIR as well. Both 13C NMR and FTIR spectra of this fraction were generally similar to the spectra of the FA fraction of soil and sewage sludge. In the POC fraction, O-alkyl and alkyl carbon were the major contributors to the 13C NMR spectra. The total nitrogen content in this fraction ranged from 21-58 g kg-1 and was about three to seven times as much as in the DOC fraction. Adsorption isotherms of DOC from vinasse on different horizons of an Ultisol indicated that DOC adsorption increased with depth. Adsorption isotherms of DOC on pure kaolinite, synthetic goethite and hematite showed that the maximum adsorption capacity of the Fe-oxyhydroxides was as much as about five times the maximum adsorption capacity of kaolinite. Concentrations of Cu, Mn, and Zn in 4M HNO3 and AAAc-EDTA extracts were higher in the "sacrificed areas" compared to the other sites. Levels of Pb were unchanged. Enrichment of most of these metals was evident up to the maximum depth of 60 cm. Sugarcane cultivation tended to reduce total carbon at the 0-20 cm depth while application of vinasse did not influence the organic matter content of these soils.