Wireline formation testers (WFT) are widely used to measure fluid pressure, to perform downhole fluid analysis in real-time, and for estimating permeability through pressure transient testing. Formation testers can measure a range of fluid properties such as color, viscosity, density, composition, pH, optical refractive index, pressure, salinity, fractional flow, and gas-oil ratio (GOR). However, WFT measurements are influenced by the process of mud-filtrate invasion because overbalanced drilling promotes radial displacement of in-situ fluids by mud filtrate. Oil-base mud (OBM) is first-contact miscible with native oil and can lead to contaminated fluid samples, erroneous estimates of petrophysical properties, and changes of composition, viscosity, compressibility, GOR, and fluid density. The objective of this dissertation is three-fold: (1) to quantify the effect of OBMfiltrate invasion on WFT measurements, (2) to estimate in-situ petrophysical properties concomitantly from transient measurements of pressure, flow rate and GOR acquired with formation testers, and (3) to quantify petrophysical, geometrical, and fluid properties that can minimize the time of withdrawal of uncontaminated fluid samples. In order to quantify the effect OBM-filtrate invasion on WFT measurements, we develop a two-dimensional axial-symmetric compositional simulator and subsequently use a commercial adaptive-implicit compositional simulator, CMG-GEM1. History matching of three field data sets acquired with probe-type formation testers in light-oil formations accurately reproduces measurements of sandface pressure, observation-probe pressure, GOR, and flow rate. Further, we demonstrate that history matching enables the detection and diagnosis of adverse data-acquisition conditions such as plugging, noisy data, and presence of OBM-filtrate invasion. We introduce a dimensionless fluid contamination function that relates GOR to fluid-sample quality. Sensitivity analysis of simulated fluid-sample quality to petrophysical properties clearly indicates that sample quality improves in the presence of anisotropy and impermeable shale boundaries. A computationally efficient dual-grid inversion algorithm is developed and tested on both synthetic and field data sets to estimate in-situ petrophysical properties from WFT measurements. These tests confirm the reliability and accuracy of the inversion technique. Results indicate that permeability estimates can be biased by noisy measurements as well as by uncertainty in flow rate, relative permeability, radial invasion length, formation damage, and location of bed boundaries. To quantify petrophysical and geometrical factors that can optimize the time of withdrawal of uncontaminated fluid samples, we compare the performance of focused and conventional probe-type WFT in the presence of mud-filtrate invasion. Simulations indicate a significant reduction in fluid-cleanup time when using a focused probe. The specific amount of improvement depends on probe geometry, fluid composition, and petrophysical properties of the probed formation. Finally, we develop an inversion method to estimate Brooks-Corey parametric saturation-dependent functions jointly from transient measurements of fractional flow and probe pressure. Results show that estimating Brooks-Corey parameters can be nonunique if the a-priori information about fluid and petrophysical properties is uncertain. However, we show that focused fluid sampling consistently improves both the accuracy and reliability of the estimated relative permeability and capillary pressure parametric functions with respect to estimates obtained with conventional-probe measurements. / text

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

This study investigated the performance of the biomass Eichhornia crassipes plant (ECP) as an additive in water-based drilling-mud. ECP is an invasive plant of fresh water ecosystems, so its use in drilling operations provides a low-cost, sustainable option that has off-site environmental benefits. Mechanical tests were conducted on ECP fibres to determine their stiffness under dried and water-wet conditions. Initial tensile tests on nylon fibre determined potential experimental artefacts with the experimental approach. The dried fibres had a water content of 8.163 wt. % (SE 0.636), whereas the wet fibres were 93.43 wt.% (SE 0.294). Water wet fibres had a lower modulus of elasticity than dried fibres and therefore, dried fibres have less tensile strength than wet fibres (Mean = 45.16 MPa; SE = 5.023; N = 41). Rheological properties of bentonite-based drilling muds amended with ECP at different concentrations were also studied. These muds were prepared by mixing ECP fragments at various concentrations (%w/w) with bentonite-water solutions and aged under ambient conditions. Mud viscosity gradually decreased with increasing shear rate, showing characteristic shear-thinning behaviour. Lost circulation of bentonite-water solutions mixed with ECP fragments were assessed with static filtration experiments. Slots and single perforated discs were designed to mimic fractures surrounding drilled boreholes. From a broad range of testing conditions, it was found that ECP fibres significantly decrease lost circulation by bridging fractures. An optimal concentration of 0.83 % by weight of ground plant stalks mixed with 6.28% bentonite in water improved rheology and filtration properties. A bridging gap model for a single fibre showed that ground stalk was less deflected than dried fibre when bridged an opening fissure. The findings of this research create an alternative to use ECP as lost circulation material in oil and gas drilling operations.

Thesis (Ph.D.)--University of Alberta, 2010. / Title from PDF file main screen (viewed on Apr. 13, 2010). A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Doctor of Philosophy, Department of Earth and Atmospheric Sciences, University of Alberta. Includes bibliographical references.

This project studied the production of barium sulphate nanoparticles through inhibition of crystal growth, during precipitation, by different surfactants. Barium sulphate is the pure form of the ore baryte, which due to its high density and softness, is the most commonly used additive used to increase the density of drilling fluids. A non-agglomerating, stable nano-scale dispersion of barium sulphate particles would have significant technical and commercial impact in the drilling fluids industry. This thesis tested the possibility of precipitating barium sulphate and restricting its crystal growth with inhibitors, creating nanoparticles. Six inhibitors were tested; dodecanoic acid, palmitic acid, stearic acid, adamantane carboxylic acid, methylnonanoic acid and a mixture of phosphate esters known commercially as Fazewet. Precipitated, inhibited barium sulphate was characterised using powder XRD, DRIFT FTIR and solid-state NMR (SSNMR). All inhibitors were shown to form single-phase, orthorhombic barium sulphate crystals proving that the inhibitors affect only the surfaces of precipitated crystals and do not enter the crystal lattice. FTIR allowed the relative adsorbed concentration of each inhibitor to be assessed. The results indicate that adsorbed inhibitor increases with increasing inhibitor concentrations but that their attachment is not proportional to the concentration. In most cases concentrations of 0.1mol l-1 of inhibitor were sufficient to saturate the crystal surface. SSNMR also agreed with this although the sample size was too small, due to equipment restrictions, to make definitive conclusions. Through the use of the Debye-Scherrer equation, the crystallite size was calculated and showed that at concentrations of 0.2mol l-1 all inhibitors other than palmitic acid produced nano-scale (< 100nm) crystallites. Further analysis showed that further reductions could be achieved through precipitation in an alkaline pH environment, with the application of mechanical shear and by using adding 50% v/v of ethanol. iv Laser diffraction particle size analysis showed that the dominant factor in reducing particle size distribution was inhibitor concentration. The volume-based PSD used by the laser diffraction system was considered to distort excessively the particle sizes present and so analysis switched to dynamic light scattering. DLS showed that dodecanoic acid, palmitic acid and stearic acid, despite forming nano-scale crystallites, could not produce a nano-scale dispersion of barium sulphate and as such were unsuitable for use in drilling fluids. Stable nano-scale dispersions were found to have been formed when inhibited with adamantane carboxylic acid, methylnonanoic acid and Fazewet. DLS also confirmed that dispersed particle size rather than simply crystallite size could be reduced with an alkaline pH and high mechanical shear. Concentration was still the dominant effect, however with the smallest particles sizes (ZAvg) being observed at concentrations of 0.6mol l-1. The particle sizes for the three modifiers were approaching that of the crystallite size, suggesting that some further reduction is possible, but large reductions are unlikely. All three inhibitors produced sub 100nm ZAvgs, with the smallest produced by methylnonanoic acid of 43nm. Spherical nanoparticles were observed through the use of ESEM and TEM. Due to equipment time restrictions only 0.2mol l-1 treatment levels could be examined, but ESEM showed apparent nanoparticle clusters, later confirmed using pixel count and SFDA methods. TEM analysis showed discrete particles as small as 3nm, indicating that the lower limit for achievable particle size may be lower than PSD measurements would suggest. The results indicate that adamantane carboxylic acid, methylnonanoic acid and Fazewet sufficiently inhibit crystal growth to be potential candidates for the production of barium sulphate nanoparticles. These three inhibitors produce a barium sulphate dispersion that is stable and nano-scale even after drying and redispersion.

No description available.

Thesis (M.Sc.)--Memorial University of Newfoundland, 2001. / Bibliography: leaves 80-94.

Thesis (M.S.)--West Virginia University, 2002. / Title from document title page. Document formatted into pages; contains x, 108 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 42-46).

Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references (leaves 301-310). Available also in a digital version from Dissertation Abstracts.

Acoustic, electromagnetic (EM), and nuclear open-hole measurements are affected by fluids saturating near-wellbore porous and permeable rock formations, including hydrocarbons, water, and mud filtrate. Fluid invasion effects can be quantified and advantageously used to estimate petrophysical properties of the invaded rock formations. This dissertation incorporates the physics of water-base mud- (WBM) and oil-base mud- (OBM) filtrate invasion to the simulation and inversion of borehole EM measurements. We assume vertical boreholes penetrating clastic hydrocarbon- or water-bearing formations subject to either WBM- or OBM-filtrate invasion. The simulation of EM measurements in the presence of mud-filtrate invasion considers three different approaches: (1) piston-like invasion profiles, where we solely consider invaded- (flushed) and virgin- (uncontaminated) zones, (2) two-phase immiscible displacement and salt mixing between the invading WBM filtrate and connate water, and (3) invasion of single or multi-component OBM-filtrate into a formation saturated with multiple hydrocarbon components wherein the individual components are first-contact miscible. The last two approaches honor the physics of mudcake growth as well as the petrophysical properties that govern the process of multi-phase, multi-component fluid-flow displacement and include the presence of irreducible, capillary-bound and movable water. Electromagnetic measurements are simulated from spatial distributions of electrical resistivity calculated from the simulations of mud-filtrate invasion using clean- or shaly-sand water-saturationresistivity models. Inversion of petrophysical properties is posed as the nonlinear minimization of quadratic objective functions that quantify the misfit between EM measurements and their simulations. In the case of WBM piston-like invasion profiles in water-bearing formations, combined inversion of array-induction resistivity and spontaneous potential (SP) measurements yields connate water electrical resistivity and Archie’s cementation exponent. Permeability is calculated from the inversion of array-induction resistivity measurements assuming immiscible fluid-flow displacement of WBM into hydrocarbonbearing formations. Accurate reconstructions of layer-by-layer permeability are primarily constrained by the availability of a-priori information about time of invasion, rate of mud-filtrate invasion, overbalance pressure, capillary pressure, and relative permeability. This dissertation also quantifies the influence of petrophysical and fluid properties on borehole resistivity measurements acquired in the presence of compositional mixing of OBM filtrate invading partially hydrocarbon-saturated rock formations. Numerical simulations of OBM-filtrate invasion are performed with an adaptive-implicit compositional formulation that allows one to quantify the effects of additional components of mud-filtrate and native fluids on EM measurements. Perturbations of petrophysical and fluid properties enable the quantification of rock wettability changes due to OBM-filtrate invasion and their effect on the simulated induction resistivity measurements. Finally, simulations of induction resistivity measurements in the presence of OBM are compared to the corresponding measurements in the presence of WBMfiltrate invasion. The latter analysis allows us to estimate a realistic flow rate of OBMfiltrate invasion that is responsible for the variation of induction resistivity measurements as a function of their radial length of response. The combined simulation of the physics of mud-filtrate invasion and EM measurements provides reliable estimates of true formation resistivity and hence of water saturation, thereby improving the assessment of in-place hydrocarbons reserves. / text