Abdulkarim, Maryam A.Muxworthy, Adrian R.Fraser, AlastairNeumaier, Martin...
15页
查看更多>>摘要：We report a detailed magnetic study of Tertiary sandstone cores from the Bittern field, West Central Graben, and Catcher Area Development (CAD), West Central Shelf, UK North Sea that identified siderite as a potential magnetic proxy for the differentiation of vertical and lateral hydrocarbon migration. Magnetic hysteresis experiments revealed increased presence of paramagnetic minerals in the oil-stained sandstones of the fields compared to the nearby dry Tertiary (unstained) sandstone of offset wells. Within the oil-stained sandstones, the paramagnetic proportion is highly variant, with low and high paramagnetic sections present. Detailed experiments including thermomagnetometry between 10 K and 900 K and XRD analysis, combined with Mo & BULL;ssbauer spectroscopy confirmed that this increase in paramagnetic response was primarily due to the formation of siderite. An increase in the quantity of paramagnetic clays and occasionally pyrite also contributed to the increased response. Siderite and iron sulphides have been interpreted to form during hydrocarbon migration and potentially oil biodegradation. We propose that hydrocarbon migration pathways may be indicated by the distribution of siderite. We argue that as hydrocarbons migrate vertically and the equilibrium partial pressure of CO2 with the environment reduces, essential HCO3- is produced which reacts with available Fe2+ to form siderite if all the other diagenetic requirements for its formation are met. The distribution of siderite and magnetic susceptibility values along the oil-stained layer provides a tool for the determination of the migration pathways in low sulphur hydrocarbon environments containing reactive iron.
查看更多>>摘要：In this paper, the impact of CO2-carbonate interactions on hydrocarbon recovery from three initially oil-saturated heterogeneous carbonate core samples (with low and mid permeabilities) were investigated. Alternate injection of carbon dioxide (CO2) and synthetic formation brine was conducted after water flooding. X-ray computed tomography scanning of the core samples before and after core flooding was performed at ambient conditions. Extent of carbonate dissolutions and rock matrix modifications were observed from the change in porosities, permeabilities, and wormhole formations. Generally, the CO2-WAG injection resulted in more than 30% extra oil recovery from the three cores after water flooding scenario. As expected, the total recovery factor of the core with lowest initial permeability and porosity was the smallest, however the core permeability increased from 1.45 mD (pre-flood) to 1987.9 mD (post-flood). Considerable amount of oil was left behind in the core with initially low permeability and porosity due to preferentially flow of WAG fluid through the wormholes, bypassing the trapped oil in the pore spaces at the uninvaded region of the rock. The study suggests that low oil recovery from core with low initial permeability and porosity is principally due to formation of wormhole because of rapid rate of rock dissolution and faster rate of CO2-carbonate reactions. Compared to the mid permeability cores, the low permeable core slows down the WAG fluid flow and give more time for CO2-carbonate rock interactions and reactions because of the tightness of the pore spaces. Thus, facilitated more exposure time and effective contact between the carbonate rock fabrics and the CO2-saturated brine.
查看更多>>摘要：Accidents play an important role in the oil and gas industry because, among other consequences, they redefine definitions of safety. One of them is the Macondo accident, which happened in 2010 and changed the industry dramatically in terms of well safety and integrity. This work provides a literature review of well safety and integrity, divided into three eras: "the past" (pre-Macondo), "the present" (post-Macondo), and "the future" (digitalization and carbon neutrality). Our goal is to highlight the changes that the industry has undergone due to this event but also due to recent trends such as digitalization and carbon neutrality. The introduction contains a glossary of relevant definitions that are widely used in these subjects. The past reviews well integrity systems that companies had before the Macondo accident, illustrating their deficiencies compared to current systems. We also present available regulations, standards, and guidelines and what changed in them due to the accident. The present reviews current well integrity management systems (WIMS), their architectures, and studies of selected well barrier elements (fluid, BOP, wellhead, rock, and primary cementing). Finally, the future reviews ongoing trends such as the use of digitalization (through digital twins) to monitor and assess well integrity and the deployment of CCUS (carbon capture, utilization, and storage) wells to achieve carbon neutrality.
查看更多>>摘要：Miscible gas injection is a proven enhanced oil recovery method for medium-light oils. Miscibility is typically assessed with the slimtube experiment, which aims at identifying the minimum pressure (MMP) above which the displacement process is multi-contact miscible and leads to low microscopic residual oil saturation. During implementation of a miscible gas injection scheme, there will often be areas close to producing wells where the reservoir pressure is below the MMP and the question then arises whether the process can still be considered miscible. Another complicating factor occurs in reservoirs with significant lateral fluid composition and pressure variations, where it is not intuitively clear how the MMP varies aerially.We employ 1D compositional reservoir simulation to investigate the impact of flowing bottom-hole pressures below MMP on the development and propagation of a miscible front. For systems with lateral fluid variation, we find that MMP is controlled by the reservoir fluid composition near the injection well as the injection gas will never actually contact the original fluid near the producer. We also find that a miscible displacement can be maintained even if the average reservoir pressure is slightly below MMP, as long as the local pressure at the gas oil front exceeds MMP. Lastly, we define the minimum density difference as the overall minimum over time of the difference between oil and gas density observed at a fixed point in the system and we demonstrate that it extrapolates towards zero linearly versus pressure for the fluid systems investigated thereby enabling determination of the dispersion-free MMP with a maximum of three pressure iterations only.
查看更多>>摘要：Condensate banking around wellbores can significantly shorten the production from gas-condensate reservoirs. Several approaches to mitigate this issue have been proposed in the literature, among which gas injection comes out with promising results. This method's efficiency has been largely investigated at core and field scales, but the underlying flow phenomena taking place at the pore-scale are still poorly understood. In order to address this gap, a compositional pore-network model was used to reproduce gas injection in a sandstone sample following condensate accumulation. C-1, C-2, CO2, N-2 and produced gas were tested as the candidates for condensate banking remediation at different pressure levels. After gas flooding, condensate saturation, heavy component recovery and gas relative permeability were quantified to appraise the achieved gas flow improvement. The results indicated that C-2 and CO2 were, overall, the most effective gases to clear the accumulated condensate and re-establish the gas flow. At high pressures, their injection reduced the liquid saturation in the porous medium at least in 80%, and restored gas relative permeabilities to values close to unity. At low pressures, however, no tested gas injection composition could reduce the condensate content in the porous medium more than 30%, contradicting the estimates based solely on liquid dropout curves. With the presented analyses, this work sets out the pioneer efforts towards an accurate pore-scale modeling of miscible gas injection in gas-condensate reservoirs.
查看更多>>摘要：To ensure a sustainable and efficient future, the foam flooding project has been paid more and more attentions to eco-friendly and high stability. Toward this effort, polysaccharides (XG) was applied together with alkyl polyglucoside (APG) to produce a highly stable foam. The properties in both surface and liquid phase were first studied in XG/APG solutions, and the specific characteristics created by XG/APG were then investigated from the aspects of bulk foam stability, coarsening behavior and foam viscoelasticity, after which the microstructure of foam films and the possible intermolecular interactions were inquired. The results indicated that the addition of XG in APG foam can enhance the performance includes both surface elasticity and liquid viscosity aspects, thus producing the high water-carried foam films and the super-low bubble coarsening as a result of the formation of complex aggregations by the hydrogen bonding. It was found that the foam half-life increases dramatically to 60min and the liquid drainage rate is reduced by 90% by adding only 0.1 wt% of XG. Furthermore, XG could successfully stabilize the foam front and substantially promote oil-displacement efficiency by producing a considerable capillary number and viscosity ratio in oil-bearing porous media during the foam flooding, which shows a great potential application in the oil recovery project.
查看更多>>摘要：Acid stimulation is one of the most common chemical approaches to overcome the reduction of crude oil pro-duction due to clogging of oil formation passages. Nonetheless, in this process, the formation of stable and tight acid in crude oil emulsions may lead to further unsolicited formation damage. In this study, the stability of dispersed HCl droplets with concentration of 15 and 28 wt % in a crude oil was characterized by means of the interaction energy theory. Similar experiments were repeated and compared with distilled water. The results showed that water droplets always tend to coalesce in short period of time, while acid droplets resist. This is due to the acid-base interaction energy, which is the most prevailing component among various interaction energies which would profoundly influence the stability of acid in crude oil emulsions. In case of using HCl solution as aqueous phase in the emulsion, this interaction between acid droplets overcomes the others, especially the attractive interactions. The most stable acid in crude oil emulsion would be formed in distances between the droplets shorter than 4 nm because acid-base interactions are short-ranged. For the investigated crude oil, it was also observed that the emulsion with HCl 28 wt % solution was more stable than that for HCl 15 wt %. Bottle tests also agreed qualitatively with the results of this theoretical approach. The practical implications of these results would be that overdosed acidizing with excessive injection rates may lead to unwanted formation damage due to formation of tight acid in crude oil emulsions. Finally, the presented results would serve as a guideline for comparing acids of different concentrations.
Safari, MehdiJye, James Wong JiunRahimi, AliGholami, Raoof...
11页
查看更多>>摘要：Nanoparticles (NPs) have been recognized as the agents that can improve the oil recovery given their positive impact on the surface wettability of rocks. However, their impacts on the interfacial tension (IFT) of the twophase fluid in a reservoir have not been widely reported. Given the significant impact of IFT on the oil recovery, it is important to develop an NPs based approach that not only alter the surface wettability but also reduce the IFT. This may be accomplished by combining nanofluids with low salinity water (LSW). In the present study, LSW and NPs are combined to study their impacts on the IFT of a two-phase flow system with water and oil. IFTs of different solutions with nano glass flakes (NGFs) and nano silica (Ns) were measured in the presence of monovalent and divalent salt ions. The results obtained were analysed using two different models as a function of time. It was found that NGFs and Ns have similar efficiency in reducing the IFT and can reveal an optimum performance once their concentration reaches 24.8% in the solution. It was observed that, unlike Ns, IFT can be further reduced by LWS in the presence of NGFs. In fact, reduction of salinity up to 3500 ppm can decrease the IFT in the NGFs solution by the salting-in effect or migration of oil components. Changing the pH of the system can also reduce the IFT, but fluctuations was observed once pH goes beyond 9. It appeared that the tension in the interface between water and oil reduces over time and the effect of adsorption time is significantly higher on the solutions with nanoparticles. It was concluded that combining NGFs with LSW not only reduces the concentration of NPs needed and can make the project economically feasible, but also favourably change the IFT during the flooding process. The findings of this study may help to understand how LSW, and nanofluids can be employed together for a better oil recovery.
查看更多>>摘要：Free radical solution polymerization method was used to preparing copolymers (FAPAM, IAPAM, and MAPAM) by copolymerizing acrylamide (AM) with functional monomers fumaric acid (FA), itaconic acid (IA) and maleic anhydride (MAH) respectively. The basic parameters of the polymer were characterized by fourier transform infrared spectrometer (FTIR), proton nuclear magnetic resonance spectroscopy (1HNMR), elemental analyzer and ubbelohde viscometer. In polymer flooding, the viscosity reduction effect of Fe2+ and S(2-)in formation water is more serious than that of inert cations, and they have greater impact on oil recovery. Therefore, this paper studied the influence of functional monomers on the structure of polymers and the influence on the resistance to Fe2+ and S(2-)properties of polymers through rheometer, gel permeation chromatography (GPC) and scanning electron microscope (SEM). The results revealed that the intra-chain or interchain forces can be increased to varying degrees by introducing different functional groups into the polymer molecular chains, as a result, the copolymer had different resistance to Fe2+ and S2-. In addition, the carboxyl groups on MAPAM chain were the most evenly distributed, its configuration was the most regular, and its resistance to Fe2+ was the strongest. Relatively, the carboxyl groups on IAPAM macromolecular chain were evenly distributed on both sides of the main chain, and it had the strongest ability to resist S2-. The results of GPC and SEM further proved that the copolymers had the ability to resist Fe2+ and S2-.
查看更多>>摘要：To understand the fracture behavior for variable density in-plane perforations on a horizontal well, true triaxial hydraulic fracturing experiments were performed with acoustic emission monitoring. The experimental results indicate that the variable density in-plane perforations can not only create transverse fractures but also arrest fracture propagation toward undesirable zones. The in situ stress and treatment parameters play significant roles in the fracture morphology and breakdown pressure. Under a large horizontal principal stress difference, there is a high possibility for simple transverse fracture creation, which results in a lower breakdown pressure. Moreover, the decrease in fracturing fluid viscosity can increase the fracture complexity and increase in pump rate can increase breakdown pressure and induce the complex fracture geomtetry. The acoustic emission (AE) characteristics and cutting fracture morphology demonstrate that not all perforations can be successfully initiated during the fracturing process. Because of the stress interaction from side perforations, fracture initiation and propagation from the middle perforation are strongly suppressed. Although the middle fracture is not fully initiated and propagated, it is still beneficial for the side hydraulic fracture connection and propagation in one plane. Secondary and axial fractures can still be observed, primarily due to the stress interaction between neighboring perforations and misalignment of the perforation tunnel orientation with the principal stress direction. In addition, the creation of complex fractures tends to occur using a high pump rate, which relates to tense fluid distribution competition from each perforation tunnel. Fracture initiation may follow an order but mostly tends to initiate from side perforations. Because of the stress interaction, hydraulic fractures from the side perforation can sometimes deviate from the perforation tunnel direction, twist and kink, and finally, generate nonplanar fractures. A large horizontal principal stress difference is recommended and beneficial for simple, straight and planar fracture creation during hydraulic fracturing stimulation with variable density in-plane completion for the horizontal well.
NSTL
Elsevier