查看更多>>摘要：Shale samples containing single pre-machined slots were tested under uniaxial compression directed along with bedding layers. Observed fractures were initiated by the slots, however, their further development was controlled by the shale bedding layers. Slots normal to the loading direction also cause fracturing and reduce failure load. The fracturing is initiated by tensile stress generated at the slot surface due to convergence of the initial open slot. Therefore, the presence of initial aperture in pre-existing cracks or fractures is capable of changing the mechanism of fracture generation. Three kinds of macroscopic fractures are observed: tensile fractures along bedding layers, shear fractures along the inclined direction, and buckling fractures at the final failure moment. Three types of microcracks are identified: shear microcracks produced from initial weak micro-planes unrelated to the bedding layers, tensile microcracks produced from the shear microcracks in the form of wing cracks, and shear microcracks induced by high uniaxial compression stress. The growth of wing cracks can be assisted by the bedding layers. The research results will contribute to the understanding of failure mechanisms of rocks containing prominent bedding layers.
查看更多>>摘要：In order to systematically study the rheological and morphological characteristics of foam fracturing fluid, hydroxylpropyl guar (HPG) was selected as the foam stabilizer, sodium dodecyl sulfate (SDS) and cetyl trimethyl ammonium bromide (CTAB) were selected as the foaming agents, and foam fracturing fluid used for coalbed methane (CBM) stimulation was prepared. The viscosity, quality and half-life of foam fracturing fluid under different additive concentration levels were tested, and the bubble morphology and its relationship with half-life were observed and quantitatively analyzed with microscopy. In addition, the influence of pulverized coal on foam stability was also studied. The results show that the influence of pulverized coal on the basic parameters of the foam fracturing fluid correlated with the particle size and concentration of the pulverized coal. The small particle size of pulverized coal increased the liquid phase viscosity and half-life of the foam, but reduced the foam quality. With increasing pulverized coal concentration, the effects were enhanced. The average bubble diameter decreased with increasing HPG concentration, and the changing trend of the bubble diameter conformed to the gamma distribution. The foam half-life had a positive and negative correlation with the bubble morphology parameters alpha and beta, respectively. The results can deepen the understanding of the influence of foaming agents, foam stabilizers, and coal particles on the properties of foam fracturing fluids, and provide a reference for the optimization of foam fracturing fluid formulations.
Hamdi, Sinan S.Alzanam, AliMohyaldinn, Mysara E.Muhsan, Ali S....
10页
查看更多>>摘要：Scale inhibition squeeze treatment is a common practice to prevent scale deposition within the downhole utilities, valve applications, and tubular components of the oil and gas producing wells. The conventional squeeze treatment has a short lifetime due to the reservoir rocks' limited adsorption of scale inhibitors and the quick desorption rate. As a result, this process has to be repeated multiple times per year, leading to massive increases in operational costs. Carbon-based nanomaterials are known for their high specific surface area, making them an attractive coating agent to enhance the capability of rocks' surfaces to adsorb chemicals such as scale inhibitors. In this paper, carbon-based nanomaterials of graphene nanoplatelet (GNPs) and three different types of carbon nanotubes (CNTs) are proposed as novel nanocoating to extend the lifetime of the conventional scale inhibitor squeeze treatment. A natural polymer of Gum Arab (GA) was used to graft the nanomaterials surfaces to ensure a homogeneous and stabilized coating solution. The adsorption of diethylenetriamine penta (methylene phosphonic acid) (DTPMP) scale inhibitor into GNPs and CNTs was investigated using a UV-Vis spectrophotometer. Various characterization techniques such as FTIR, Raman spectroscopy, and XPS were performed to evaluate the interaction between DTPMP and the proposed nanocoating (GNPs/CNTs). Based on UV-Vis results, GNPs was found to be the optimal coating agent with an adsorption capacity of 135 mg/g at ambient temperature and 114 mg/g at 96 degrees C. Its coating gets saturated with DTPMP within 1 h of interaction. Increasing the initial scale inhibitor concentration was found to increase the adsorption capacity of GNPs. Based on the core flooding conducted on Berea sandstone, the injection of nanocoating into the core sample reduces the permeability by only 12%. Finally, the injected nanomaterial was safely transported through the core, and the primary retention mechanism was adsorption rather than physical filtration/plugging.
Roshan, HamidLv, AdelinaAghighi, Mohammad AliSarmadivaleh, Mohammad...
9页
查看更多>>摘要：Detachment of clay particles from clay-rich interburdens is the main source of solid production in coal seam gas wells (CSG), costing the Australian operators millions of dollars every year. Several techniques have been proposed to reduce the solid production and consequent pump failure in already constructed open hole/slotted liner wells. Amongst all remedial techniques for these existing problematic wells, chemical stabilization seems to be the most practical method. The high cost of chemical additives, their environmental issues, potential low effectiveness and technical difficulties for their placement downhole have, however, hindered their wide application. In particular, the long-term effect of current chemical additives on interburden stability and their influence on coal seam matrix gas diffusion need further investigation. In this study, the application of colloidal silica nanoparticle solution (silica SOL) as a long-term chemical stabilization method for clay-rich interburden in CSG wells was investigated. A series of comprehensive experiments were performed to investigate the effect of the silica SOL on stability of pure compacted dry smectite clays and clay-rich sandstone samples in stationary and turbulent conditions (resembling the wellbore condition during gas production) using a uniquely designed experimental setup. Additionally the effect of silica SOL on coal and its gas adsorption was analyzed. The results of this study demonstrated that the silica SOL is a suitable candidate for long-term chemical stabilization of clay minerals as a cost-efficient and environmentally friendly additive. Its non-reactivity with coal and its inert response on gas sorption is another significant benefit of the proposed chemical solution.
查看更多>>摘要：Multi-objective production optimization (MOPO) which aims at finding an optimal well control scheme is regarded as a win-win strategy for improving economic and production gains. Generally, the MOPO processes involve computationally expensive numerical simulations and high-dimensional decision variables which limit their application to actual reservoir optimization problems. Surrogate-assisted multi-objective optimization method which uses a simple yet efficient approximation model shows huge potential in solving production optimization problems since it lessens the computational burden by decreasing the use of computationally expensive numerical simulations. In this paper, a novel self-adaptive multi-fidelity surrogate-assisted (SAMFS) multi-objective production optimization algorithm (SAMFS-MOPO) is proposed to reduce the computational burden and enhance the accuracy of the surrogate model. A similar method has been applied to well spacing optimization but the uniqueness of this method is that two fidelity samples are used to establish a multi-fidelity (MF) surrogate model, while i-updating and g-updating strategies are used to renew the MF surrogate model during the optimization process so as to improve its accuracy and reduce the computational burden. To the best of our knowledge, this is the first time a self-adaptive multi-fidelity surrogate model is used for production optimization. Furthermore, three classic multi-objective benchmark problems and two reservoirs with different complexities were applied to illustrate the effectiveness and accuracy of the proposed SAMFS-MOPO method. It was found that the SAMFS-MOPO method had superior performance in convergence, diversity, and efficiency than other conventional methods.
查看更多>>摘要：To avoid premature operational failure of the ESP systems, their vibration levels must be evaluated for acceptance before installation. The vibration assessment of Electrical Submersible Pump (ESP) systems and other rotating machines considers that the most important amplitude occurs in the radial orientation. Typical vibration amplitude estimation uses radial orthogonal sensors and considers the maximum vibration amplitude between the two sensor signals. However, this approach does not account for the orbit's shape, leading to an error up to 41,4% between the maximum estimated amplitude in each sensor and the maximum radial vibration amplitude, the orbit semi-major axis. This paper proposes a method to generate a frequency spectrum with invariance to the shape of the vibration orbit, namely the Orbit Semi-major Axis Spectrum. The proposed method is compared to the typical vibration amplitude estimation approach using individual sensor signals and the Full Spectrum method. The methods are applied on vibration signals from two pumps at different wear states, and results are analyzed. The estimation error of the vibration amplitude in ESP systems due to disregarding the shape of the vibration orbits is shown. The results indicate that the proposed method presented the maximum radial vibration amplitudes of each orbit frequency component (orbit semi-major axis), which is not directly possible with the Full Spectrum and is impossible with the individual frequency spectrum. The orbit semi-major axis amplitudes of the pumps were up to 28% higher than the maximum amplitude estimated from the individual orthogonal sensors.
查看更多>>摘要：The accurate and in-time prediction of gas condensates dew point pressure (PDew) is of great importance regarding the technical and economic points of view for fluid characterization, reservoir performance calculations, planning the development of gas condensate reservoirs, and design and optimization of production systems. Although the laboratory tests provide the most accurate and reliable results, it is an expensive and timeconsuming process sometimes associated with some errors. Artificial intelligence-based methods have emerged as promising tools in different aspects of engineering. In this study, after a thorough analysis of the gas condensate data samples, the application of different intelligent modeling is investigated. A databank of 721 data samples is gathered, and different intelligent methods approaches are used for modeling. The results of three different data mining methods are combined using Committee Machine Intelligent Systems (CMIS) in an attempt to receive more accurate results. Three different methods of arithmetic, geometric, and harmonic approaches are utilized to develop the CMIS model. It was concluded that the harmonic CMIS yields the best predictions by average absolute relative deviation (AARD) and R2 values of 3.456% and 0.9702, respectively. This novel CMIS model could successfully outperform all the developed initial models. Additionally, a literature review showed that the proposed model could outperform the previously published models including artificial intelligence, equation of state, and correlation-based method considering both prediction accuracy and data coverage.
Sadeghtabaghi, ZahraRabbani, Ahmad RezaHemmati-Sarapardeh, Abdolhossein
11页
查看更多>>摘要：The level of crude oil thermal maturity has so far been done using biomarker ratios. Despite valuable geochemical information provided by biomarker ratios, they usually face problems in thermal maturity assess-ment. This paper aims to introduce new indexes for thermal maturity assessment. For this purpose, three crude oil samples were heated at 100 degrees C for a while and then sampled. The asphaltene fractions of heated samples were analyzed by XRD and FTIR methods after precipitation. The variations of derived indexes from diffractograms and spectra indicate that aromaticity, the average diameter of aromatic sheets, and branched index increase during the heating process. In contrast, the average height perpendicular to the aromatic sheets and subsequently the average number of aromatic sheets decrease. Since these variations are concerning time and temperature, they can be considered as thermal maturity indicators. These alterations are also consistent with previous re-searches. In this paper, the thermal maturity of eight Iranian crude oil samples, which biomarker ratios were unable to determine their thermal maturity level, has been assessed using these novel indicators for the first time. These crude oil samples belong to three distinct genetic groups, and thermal maturity has been evaluated in all families. In the first genetic group, the Fahliyan reservoir has more mature crude oil samples than the crude oil sample of the Kazhdumi reservoir. In the second group, the Buwaib sample possesses more maturity level than Khatiah crude oil. Eventually, the Sarvak reservoir contains more mature crude oil than two other Kazhdumi samples. The final results are compatible with the other data, such as reservoir depth and API.
查看更多>>摘要：The three-stage acid fracturing technology is an effective technology for tight sandstone reservoirs with undeveloped natural fractures. Its filed test has achieved good results in the tight sandstone field test in the Daning block of China. The core of this technology is to complete the pump injection procedure of "conventional fracturing, acid fracturing and conventional fracturing" in sequence. However, fracture propagation behaviors vary greatly under different acidizing fracturing conditions. In this paper, the influence of different factors on the uneven degree of hydraulic fracture etching and fracture propagation was studied by triaxial hydraulic fracturing physical simulation experiment. The effects of different acid concentration, acid dosage and acid reaction time on fracture propagation behaviors were analyzed. The results show that the fractures formed by the fracturing with displacement of 160 mL/min in the laboratory did not penetrate the overburden and underburden, and longer fractures and small branch fractures were formed in the reservoir. Hydraulic fractures showed a trend of continuous expansion in the sandstone reservoir, indicating that the fracturing effect was favorable. The experimental displacement is converted to the field displacement of 8 m(3)/min. The influence degree of acid concentration, acid dosage, acid reaction time on fracture propagation of three-stage acidizing fracture decreases in turn. Acid concentration and acid dosage are positively correlated with the area of fracture propagation. The influence of acid injection reaction time on fracture propagation is the lowest, and the influence of acid injection reaction time on fracture propagation area is significant only in the case of high acid dosage or high acid concentration. The influence of acid immersion time on fracture permeability is far less than that of acid concentration on fracture permeability. However, the greater the acid concentration, the greater the impact of acid immersion time on fracture permeability. The experimental results can provide empirical reference for the onsite construction of the three-stage acid fracturing in tight sandstone reservoirs.
查看更多>>摘要：Stimulated reservoir volume (SRV) is the most critical index to represent the hydraulically fractured volume after stimulation. The existing models using microseismic events usually lack a sufficient unified basis on the geo-metric definition, leading to significant differences in SRV calculation and interpretation. This paper has generally conducted the classification and the evaluation for the existing models and the newly proposed model. According to three typical grid structures, we firstly divided SRV models into three categories: boundary-based, voxel-based, and density-based. Three typical SRV calculation methods are also proposed based on the alpha shape method, the voxel discretization, and the octree decomposition. Then, we have developed an integrated workflow based on synthetic events to evaluate their performance quantitatively under different fracture configurations and noise ratios. Through a large number of simulated calculations, it is indicated that the density-based method outperforms the other two methods in accuracy, adaptability, and anti-noise ability for complex fracture networks with different configurations. Besides, the engineering application has also its practicability and superiority in generating more refined grid structures. This paper attempts to summarize and evaluate the existing methods and proposes new methods based on the classification. It would provide helpful guidance for developing more superior SRV calculation methods.
NSTL
Elsevier