Specially designed non-damaging lost circulation pills (LCP) are being effectively applied for drilling depleted zones worldwide. Optimizing the LCP compositions stop the lost circulation effectively and protect the production zone from liquid and solids invasion significantly. Shape, particle size distribution and concentration of the lost circulation materials (LCM) are key parameters determining the effectiveness of LCP. In this study, the Permeability Plugging Apparatus (PPA) is utilized to evaluate effectiveness of various LCM&rsquo / s in curing the lost circulation. Sized calcium carbonates are used as LCM in different concentrations and in different particle size distribution. Lost circulation zones are simulated using the ceramic disks and slotted disks. Ceramic disks with nominal pore sizes 20, 35, 60, 90, and 150 microns are characterized in terms of pore size distribution using the computerized image analysis technique. Filter cake quality, spurt loss and filtrate volume are basic parameters to be evaluated in this study. Tests are performed at 75 F and 300 psi of differential.

Shallow water flow and lost circulation are frequently encountered problems during drilling top holes of oil, gas or geothermal wells. Plenty of methods have been applied to overcome these problems. Placement of silicate based gel systems is one of the oldest methods to seal such undesired zones. For this study, sodium-silicate based gel system is investigated experimentally. This gel system is deliberately delayed multi-component system mixed as a uniform liquid at the surface but desired to form strong gel where it is placed in the well. The experimentally analyzed system is composed of distilled water, sodium-silicate solution, polymer solution, lost circulation materials, weighting agent and organic initiator. In this study, effect of these components on gel time, gel quality and gel strength at room temperature is investigated as a function of their concentration. To be able to compare gelation time of different compositions, gel time tests were performed by following the developed method in this study. Observation codes were defined to be able to compare the gel qualities of different compositions. For gel time and quality tests, sodium-silicate concentrations from 3.5% to 15% were studied and the concentrations between 7.5% and 10% were found as optimum. Gel time is getting higher as silicate-initiator ratio (SIR) increases for these optimum concentrations. It was also determined that, addition of polymers reduces the gel time and increases the elasticity of the resulting gels. Long term gelation process was investigated by monitoring turbidity (NTU) of the mixtures and plotting NTU versus time curves. Viscosity development curves obtained from rotational viscometer at various constant shear rates indicated reduced gelation times with increasing shear rate. Furthermore, by using modified High-Pressure, High-Temperature filter press cell, it was determined that, addition of lost circulation materials increases the extrusion pressure.

This thesis addresses the application of xanthan/borate gel for lost circulation treatment. Steady shear viscometry method was applied in which the gel system was under constant shear rate while apparent viscosity was being recorded. The apparent viscosity was constant up to initial gelation time in which viscosity started to build up. Four parameters: initial and final gelation times as well as initial and final viscosities are defined and a correlation is derived between those parameters and four variables: polymer blended with crosslinker, pH-controller, and magnesium chloride concentration as well as temperature. These correlations can help the drilling industry to manage the lost circulation treatment job in a way to have enough time and pressure to pump the fluid and to optimize the time and quality required for final gel. The effects of those variables besides mixing time and shear history on gelation were also investigated. Temperature and pH-controller shortens initiation of gelation. Poly-cross shifts viscosity upward. Retarder postpones the final gelation time. Shear history does not affect initial gelation time and increase of mixing time reduces initial gelation time. This thesis also investigates the rheological model behavior of this gel system before initial gelation time which is the time allowed for pumping the fluid. Shear stress was measured at 0.1,1,50, and 450 rpm besides the conventional readings. Then residual mean squares for six common rheological models were obtained. Sisko was found to be the best fitting model based on this statistical approach. Moreover a modified Bingham-plastic and low shear yield point model are suggested.

Drilling is crucial to many industries, including hydrocarbon extraction, CO2 sequestration, geothermal energy, and others. During penetrating the subsurface rocks, drilling fluid (mud) is used for drilling bit cooling, lubrication, removing rock cuttings, and providing wellbore mechanical stability. Significant mud loss from the wellbore into the surrounding formation causes fluid lost-circulation incidents. This phenomenon leads to cost overrun, environmental pollution, delays project time and causes safety issues. Although lost-circulation exacerbates wellbore conditions, prediction of the characteristics of subsurface formations can be obtained. Generally, four formation types cause lost-circulation: natural fractures, and induced fractures, vugs and caves, and porous/permeable medium. The focus in this work is on naturally fractured formations, which is the most common cause of lost circulation. In this work, a novel prediction tool is developed based on analytical solutions and type-curves (TC). Type-curves are derived from the Cauchy equation of motion and mass conservation for non-Newtonian fluid model, corresponding to Herschel-Bulkley model (HB). Experimental setup from literature mimicking a deformed fracture supports the establishment of the tool. Upscaling the model of a natural fracture at subsurface conditions is implemented into the equations to achieve a group of mud type-curves (MTC) alongside another set of derivative-based mud type-curves (DMTC). The developed approach is verified with numerical simulations. Further, verification is performed with other analytical solutions. This proposed tool serves various functionalities; It predicts the volume loss as a function of time, based on wellbore operating conditions. The time-dependent fluid loss penetration from the wellbore into the surrounding formation can be computed. Additionally, the hydraulic aperture of the fracture in the surrounding formation can be estimated. Due to the non-Newtonian behavior of the drilling mud, the tool can be used to assess the fluid loss stopping time. Validation of the tool is performed by using actual field datasets and published experimental measurements. Machine-Learning is finally investigated as a complementary approach to determine the flow behavior of mud loss and the corresponding fracture properties.

Made available in DSpace on 2014-12-17T14:07:09Z (GMT). No. of bitstreams: 1 Marcus VCB_DISSERT_PARCIAL.pdf: 2643130 bytes, checksum: 5d46e76949be4c4eb0ad9dfdafb24bcb (MD5) Previous issue date: 2013-02-18 / The materials engineering includes processes and products involving several areas of engineering, allowing them to prepare materials that fulfill the needs of various new products. In this case, this work aims to study a system composed of cement paste and geopolymers, which can contribute to solving an engineering problem that directly involves the exploitation of oil wells subject to loss of circulation. To correct it, has been already proposed the use of granular materials, fibers, reducing the drilling fluid or cement paste density and even surface and downhole mixed systems. In this work, we proposed the development of a slurry mixed system, the first was a cement-based slurry and the second a geopolymer-based slurry. The cement-based slurry was formulated with low density and extenders, 12.0 ppg (1.438 g/cm ?), showing great thixotropic characteristics. It was added nano silica at concentrations of 0.5, 1.0 and 1.5 gps (66.88, 133.76 and 200.64 L/m3) and CaCl2 at concentrations of 0.5, 1, 0 and 1.5%. The second system is a geopolymer-based paste formulated from molar ratios of 3.5 (nSiO2/nAl2O3), 0.27 (nK2O/nSiO2), 1.07 (nK2O/nAl2O3) and 13.99 (nH2O/nK2O). Finally, we performed a mixture of these two systems, for their application for correction of circulation lost. To characterize the raw materials, XRD, XRF, FTIR analysis and titration were performed. The both systems were characterized in tests based on API RP10B. Compressive strength tests were conducted after curing for 24 hours, 7 and 28 days at 58 ?C on the cement-based system and the geopolymer-based system. From the mixtures have been performed mixability tests and micro structural characterizations (XRD, SEM and TG). The results showed that the nano silica, when combined with CaCl2 modified the rheological properties of the cement slurry and from the concentration of 1.5 gpc (200.64 L / m?) it was possible to obtain stable systems. The system mixture caused a change in the microstructure of the material by favoring the rate of geopolymer formation to hinder the C3S phase hydration, thus, the production of CSH phases and Portlandite were harmed. Through the mixability tests it can be concluded that the system, due to reduced setting time of the mixture, can be applied to plug lost circulation zones when mixed downhole / A engenharia de materiais abrange processos e produtos envolvendo v?rias ?reas da engenharia, permitindo que sejam preparados materiais que atendam a v?rias necessidades de novos produtos. Neste caso, este trabalho tem por objetivo estudar um sistema de pasta composto por cimento e geopol?meros, que possa contribuir para a resolu??o de um problema de engenharia que envolve diretamente a explora??o de po?os de petr?leo sujeitos ? perda de circula??o. Para corrigi-la, j? foi proposto na literatura o uso de materiais granulares, fibrosos, redu??o da densidade do fluido de perfura??o ou pasta de cimento e at? mesmo sistemas mistos de fluidos misturados na superf?cie ou no fundo do po?o. Neste trabalho, foi proposto o desenvolvimento de um sistema misto de pastas, sendo o primeiro ? base de cimento Portland e o segundo ? base de geopol?mero. A pasta ? base de cimento, foi formulada com baixa massa espec?fica e aditivos extendedores, 12,0 lb/gal (1,438 g/cm?), apresentando grande car?ter tixotr?pico. Essa pasta foi aditivada com nanoss?lica, em concentra??es de 0,5; 1,0 e 1,5 gpc (66,88; 133,76 e 200,64 L/m3) e CaCl2, em concentra??es de 0,5; 1,0 e 1,5 %. A segunda pasta se constitui ? base de geopol?mero, sendo formulada a partir das raz?es molares de 3,5 (nSiO2/nAl2O3); 0,27 (nK2O/nSiO2); 1,07 (nK2O/nAl2O3) e 13,99 (nH2O/nK2O). E por fim, foi realizada a mistura desses dois sistemas, visando sua aplica??o para corre??o de perda de circula??o. Para caracterizar os precursores foram utilizadas as t?cnicas de DRX, FRX, FTIR e titula??o. Foram realizados os ensaios de caracteriza??o baseados na API RP10B para ambas as pastas puras. Ensaios de resist?ncia ? compress?o foram realizados ap?s a cura por 24 horas, 7 e 28 dias ? 58 ?C, para os sistemas de pasta de cimento e geopol?mero, separadamente. A partir das misturas, foi realizado o ensaio de misturabilidade e caracteriza??es microestruturais (DRX, TG e MEV). Os resultados mostraram que a nanoss?lica, quando combinada ao CaCl2 modificou as propriedades reol?gicas da pasta de cimento e a partir da concentra??o de 1,5 gpc (200,64 L/m?) foi poss?vel se obter sistemas est?veis. A mistura dos sistemas ocasionou uma modifica??o da microestrutura do material, atrav?s do favorecimento da rea??o de geopolimeriza??o em detrimento da hidrata??o da fase C3S, com isso, a produ??o das fases Portlandita e C-S-H foram prejudicadas. Atrav?s dos ensaios de misturabilidade, devido ao reduzido tempo de pega das misturas, pode-se concluir que o sistema misturado, pode ser aplicado para tamponar zonas de perda de circula??o quando misturado no fundo do po?o