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Piazza, Ralph (Petrobras) | Vieira, Alexandre (Petrobras) | Sacorague, Luiz Alexandre (Petrobras) | Jones, Christopher (Halliburton) | Dai, Bin (Halliburton) | Price, Jimmy (Halliburton) | Pearl, Megan (Halliburton) | Aguiar, Helen (Halliburton)
Abstract This paper presents a new optical sensor configuration using a multivariate optical computation (MOC) platform in order to enhance chemical analysis during formation tester logging operations. The platform allows access up to the mid-infrared (λ ~ 3.5 microns) optical region, which has previously not been accessible for in-situ real-time chemical measurements in a petroleum well environment. The new technique has been used in the field for the analysis of carbon dioxide and synthetic drilling fluid components such as olefins. MOC is a technique that uses an integrated computational sensor to perform an analog dot product regression calculation on spectroscopic data, optically, rather than by electronic digital means. Historically, a dot product regression applied to spectroscopic data requires both a spectrometer and a digital computer in order to perform a chemical analysis. MOC sensors require neither and because the key sensor component, the multivariate optical element (MOE), is a stable temperature robust solid-state element, the technique is well suited for downhole petroleum environments. A new dual-core configuration using two MOEs designed to work in parallel enhances the sensitivity of the measurement enabling a mid-infrared analysis. Spectroscopic measurements were performed on 32 base oils that were reconstituted to reservoir compositions over a wide temperature and pressure range up to 350°F and 20,000 psi for a total of 12 combinations for each base oil. Live gas compositions (i.e. reservoir conditions) were achieved by adding multiple methane, ethane, propane, and carbon dioxide charges to each base fluid. The reconstituted petroleum fluids were further mixed with olefin-based synthetic drilling fluid (SDF). This rigorous experimental design data therefore allowed for solid state MOEs to be designed to operate under the same reservoir conditions. Laboratory validation showed measurement accuracy of +/-0.43 wt% for a range of 0 to 16 wt% CO2 and +/-0.4% from 0 to 10 wt% SDF. A wireline formation tester optical section was modified with the MOC dual-core configuration to enable the mid infrared detection of both carbon dioxide and olefins. This formation tester was then deployed in five wells collecting seven samples from various locations. The downhole SDF and carbon dioxide measurements were subsequently found to be in good agreement with laboratory analysis with field results for valid pumpouts showing an accuracy of 0.5 wt% CO2 and 1.0 wt% olefins cross a range of 1.2 to 22 wt% CO2 and 1.4 to 9.7 wt% SDF. Carbon dioxide is an important component of petroleum whose presence and concentration affects completion options, surface facilities, and flow assurance, which thereby affects operational costs of petroleum production. Olefins are a primary component of synthetic drilling fluid (SDF), although other mid-infrared active components such as esters, ketones, alcohols, and amines also can be present. High concentrations of SDF in openhole formation tester samples lower the quality of laboratory phase behavior analysis and thereby force greater monetary risk in development of assets, especially when conducting reservoir production simulations. Therefore, it is important to monitor both components during formation tester sampling operations.
Abstract Technological advancement in sensors, digital electronics and wireless communications have enabled development of low cost and low power wireless sensors and networks, thereby enabling a paradigm shift in autonomous monitoring and control for a wide range of applications in the oil and gas industry. These applications can be found all across the industry including supply chain, refineries/petrochemical plants, pipelines, exploration, drilling, production and transportation. One of the challenges is powering up these sensor/control devices. Despite the ultra-low power consumption of wireless nodes and the high energy density of batteries, they still have limited stored energy and, therefore, a limited lifetime. In many scenarios, the battery replacement of sensors could be a very time consuming task and even uneconomical and unmanageable. To tackle these issues and enable fully autonomous and maintenance free wireless sensing and control, a continuous source of energy is required. We have investigated Energy Harvesting as the potential solution for providing reliable and long-term power for sensors by scavenging various ambient energy sources such as environmental/machine vibrations, thermal sources, flow, solar, wind energy and converting it to useable electrical energy. This paper provides a survey of energy harvesting techniques including mechanical (piezoelectric, electrostatic, electromagnetic and magentostrictive), thermal (thermoelectric, pyroelectric), light, and various state-of-the-art technologies. The requirements and technical challenges, along with financial drivers and benefits, are addressed. Various ambient energy sources present at the surface and their usage for different applications in the oil and gas industry are identified and discussed in detail. Finally, recommendations are made for improvement and achieving the goal of practical implementation of energy harvesting to enable self-powered remote and wireless monitoring and control in oil and gas. Although the energy harvesting market is rapidly increasing because of its growing demand in various industries, the technology hasn’t been thoroughly investigated for oil and gas applications.
Abstract High-molecular-weight crosslinked polymer fluids have been used to stimulate oil and gas wells for decades. These fluids exhibit exceptional viscosity, thermal stability, proppant transportability, and fluid leak-off control. However, a major drawback of crosslinked polymer fluids is the amount of polymer residue they leave behind. Polymer residue has been shown to significantly damage formation permeability and fracture conductivity. 1–3 Recently, viscoelastic surfactant (VES) fluids composed of low-molecular-weight surfactants have been used as hydraulic fracturing and frac-packing fluids. The surfactants structurally arrange in brine to form rod-like micelles that exhibit viscoelastic fluid behavior. VES fluids, once broken, leave very little residue or production damage. However, excessive fluid leak-off and poor thermal stability has significantly limited their use. This paper will introduce newly developed, select nano-size crystals with unique surface charges and will explain how nanoparticle technology pseudo-crosslinks VES rod-like micelles together to improve the fluid loss control and proppant transport of VES fluids to a performance level similar to that of crosslinked polymer fluid. The nanoparticle pseudocrosslinked VES micelle fluid develops a wall-building pseudo-filtercake on the face of porous media to control fluid loss. When internal breakers are used to degrade the VES micelle structures the leaked-off VES fluid and the pseudo-filtercake breaks into brine water and nanoparticles. Since the nanoparticles are very small and readily pass through the pores of greater than 0.1 md formations, they are flowed back with the produced fluids, and no internal or external "solids" damage is generated. This paper will present laboratory data that shows how uniquely charged nanoparticles improve VES fluid rheology, leak-off control, and proppant suspension. Also presented are test results comparing nanoparticle enhanced VES to borate crosslinked guar polymer fluids. The mechanisms that enhance the performance of these fluids also will be discussed. Introduction Crosslinked polymer fluids (CPF) are the most common type of fluid used for hydraulic fracturing. These fluids can achieve high viscosities with low leak-off rates for a wide range of reservoir temperatures and permeabilities. With their efficient leak-off control, CPF can be used to generate excellent fracture geometry in most reservoirs. They also have excellent proppant suspension and placement capability. However, CPF have an inherent weakness that decades of developing internal breaker technologies have not been able to resolve: this weakness is the amount of fracture conductivity damage that occurs due to incomplete crosslinked-polymer filtercake removal from the fracture. A recent Joint Industry Project study has showed that polymeric filtercake thickness, and its yield stress, is one of the primary culprits to poor fracture cleanup and fracture conductivity loss when using crosslinked polymer fluids. 4
This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper SPE 113533, "Performance Enhancements of Viscoelastic- Surfactant Stimulation Fluids With Nanoparticles," by James B. Crews, SPE, and Tianping Huang, SPE, Baker Hughes, originally prepared for the 2008 SPE Europec/EAGE Conference and Exhibition, Rome, 9-12 June. The paper has not been peer reviewed. The full-length paper introduces newly developed, select nanosized crystals with unique surface charges and explains how nanoparticle technology pseudocrosslinks viscoelastic surfactant (VES) rod-like micelles together to improve the fluid-loss control and proppant transport of VES fluids to a performance level similar to that of a crosslinked-polymer fluid (CPF). The nanoparticle-pseudocrosslinked VES-micelle fluid develops a wall-building pseudofilter cake on the face of porous media to control fluid loss. Introduction CPFs are the most common type of fluid used for hydraulic fracturing. These fluids can achieve high viscosities with low leakoff rates for a wide range of reservoir temperatures and permeabilities. With their efficient leakoff control, CPFs can be used to generate excellent fracture geometry in most reservoirs. They also have excellent proppant-suspension and -placement capability. However, one weakness of CPFs is the fracture-conductivity dam-age that occurs as a result of incomplete crosslinked-polymer filter-cake removal from the fracture. Over the past decade, classical VES-fluid systems have been used for frac packs and conventional hydraulic fracturing. The composition of these fluid systems typically has been fresh water, salt [such as 4% potassium chloride (KCl)], and VES product. The classical VES-fluid systems have viscosity-dependant leakoff control into porous media and do not develop or leave filter cake on a fracture face. The advantage of this type of leakoff control is that no filter-cake damage occurs in the fracture. However, a disadvantage is that a significantly high amount of whole-gel leakoff occurs into the formation during a treatment, and most often insufficient treatment fluid remains in the fracture for generating proper fracture geometry. Additionally, no internal breaker technology has existed for VES systems until recently. The reliance on the external breaking mechanism has resulted in too frequent poor and incomplete VES-fluid cleanup from the treated reservoir. Crosslinked Polymer vs. Pseudocrosslinked Micelles Two key parameters for crosslinking polymers in an aqueous medium is the molecular weight of the polymer and the degree of polymer overlap. The more polymer overlap there is, the more intrapolymer (polymer-to-polymer) crosslinking that can occur. In almost all cases, crosslinking polymers significantly improves performance properties for hydraulic fracturing, such as much higher fluid viscosity, improved thermal stability, better proppant transport, and lower rate of fluid leakoff.