查看更多>>摘要：After the investigations of experiments and Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, the adhesion energy model was proposed to solve the discrimination of the minimum oil-gathering temperature of transportation (adhesion temperature, AT). The results of AT were in good agreement with the experimental results (error values around 0.1 °C~(-1).2 °C). And a 100-day cooling transportation test was conducted safely, indicating that the model was suitable for engineering application. It was found that the oil droplets were adhered to the initial adhesion layer on the pipeline wall by the dominant contribution of van der Waals (VDW) energy. In contrast, the electric double layer (EDL) energy can resist the coalescence between oil droplets and the initial adhesion layer. And the effects of different temperatures, oil droplet particle sizes, and salinity on the DLVO interaction energy were also analyzed. Furthermore, the effect of DLVO energy on the adhesion of heavy oil was obtained by combining the relationship between adhesion mass and AT.
查看更多>>摘要：Energy demand is increasing worldwide and shale gas formations have gained increasing attention and have become crucial energy sources. Therefore, accurate determination of shale gas-in-place (GIP) is vital for a successful production plan. Since most of the gas in shale formation is in the form of adsorbed gas, the determination of methane adsorption capacity is a very important task. In this study, two rigorous data-driven techniques, namely gene expression programming (GEP) and group method of data handling (GMDH), were utilized to provide accurate and reliable explicit mathematical expressions for predicting methane adsorption. For this purpose, a comprehensive database involving 352 data points was gathered from the literature. Pressure, temperature, moisture, and total organic carbon (TOC) were employed as input variables for the implemented correlations. Results indicate that both correlations can provide accurate predictions. However, the GEP-based correlation exhibits more reliable predictions for methane adsorption with a correlation coefficient of 0.9837. Moreover, it was shown that GEP-based correlation can accurately predict the variation of shale gas capacity for the alteration of inputs. Further, it was revealed that methane adsorption is highly dependent on moisture value, while temperature, TOC, and pressure are the most influential variables after moisture. The results of this study shed light on the power of GMDH and GEP modeling approaches, and show that these models can be employed to provide accurate and simple-to-use correlations for estimating methane adsorption in shale gas formations.
查看更多>>摘要：To achieve high-efficiency drilling in hard formations, the rotary percussive drilling tool was designed to improve rock-breaking efficiency. Currently, few studies are conducted to analyze the relationship between the percussion parameters and rock breaking efficiency, considering the dynamic characteristics of rock during rock breaking. According to this situation, to quantify the influence of different percussion parameters on the rock-breaking efficiency, a series of dynamic experiments on hard rock and numerical simulations were carried out. Orthogonal experiments of split Hopkinson pressure bar (SHPB) device were conducted to analyze 13 parameters of the Riedel Hiermaier Thoma (RHT) material model. A polycrystalline diamond compact (PDC) cutter was selected as the research object, and a corresponding numerical model was established, considering the actual size of the drilling teeth and the load transmitted to the formation. Subsequently, the numerical simulation results of the SHPB test and cutting experiment were verified using the physical model. A sensitivity analysis was carried out to analyze the effect of different factors, including dynamic amplitude, frequency, and waveform, on the penetration depth and eroded volume fraction of formation. The results proved that rotary percussion drilling increased the penetration depth and eroded volume fraction of hard rock. The rock-breaking efficiency of the square wave was more obvious than that of the triangular and sine waves. Increasing the dynamic to static load ratio was beneficial for increasing the penetration depth and eroded volume fraction of formation. When the frequency increased, the cutting section became smoother, and the cuttings were finer, which was beneficial in cleaning the borehole.
查看更多>>摘要：The efficacy of surfactant flooding as a Chemical Enhanced Oil Recovery (EOR) method depends on the amount of the surfactant loss in the porous medium. Adding alkali to surfactant-polymer (SP) floods lowers surfactant adsorption/retention, but alkali has several key challenges that prevent operators from adopting it as the universal chemical EOR technique. Sodium polyacrylate has been successfully used as a sacrificial agent to reduce surfactant adsorption in static and dynamic adsorption tests. In this study, we evaluated the effect of sodium polyacrylate in Berea sandstone in the presence/absence of petroleum crude oil and compared dynamic adsorption/retention values with and without NaPA. Prior to corefloods, ultra-low interfacial tension surfactant formulations were identified using microemulsion phase behavior experiments for two different crude oils. Corefloods were conducted at corresponding optimum salinity of the surfactant formulations with a negative salinity gradient towards polymer drive. Surfactant concentration in effluent was measured by a high-performance-liquid-chromatography method (HPLC), and the adsorption/retention values were calculated by material balance. In our experiments, surfactant adsorption during single-phase corefloods (in the absence of crude oil) in Berea sandstone cores was found to be around 0.17-0.23 mg/g-rock;; addition of a 0.5~(-1).0 wt % sodium polyacrylate decreased surfactant adsorption to 0.10 mg/g-rock. Surfactant retention in SP oil recovery corefloods in Berea sandstone cores without and with NaPA was found to be 0.20 mg/g-rock and 0.11 mg/g-rock, respectively.
查看更多>>摘要：The topology of induced fractures by hydraulic fracturing is important for well performance in unconventional low-permeability reservoirs. Natural fractures are a common feature in geological formations and are preferred failure paths during hydraulic fracturing. Therefore, the interaction of hydraulic fractures and natural fractures is fundamental to the fracture growth in fractured reservoirs. Field observations of induced fracture systems show modeling fracture complexity to be needed for improving completion design and interpreting stimulated reservoir volume. In this study, a finite discrete-element model is presented to investigate multifracture propagation in fractured reservoirs. The numerical model captures the fracture complexity including branched, stranded, and kinked fractures, as well as offset crossing of natural fractures. The results show biased fracture growth in the fractured reservoir, which demonstrates the impacts of rock heterogeneity on multifracture propagation. This work also emphasizes the control of fluid partition at the wellbore and among the intersecting fractures. Fluid partition at the wellbore is found to be a major challenge to the completion design of tight cluster spacing, which has been shown to improve production in recent years.
查看更多>>摘要：To quantitatively evaluate the pore size distributions (PSD) contributed by various components (PSDCVC) in over-mature shale samples, the Upper Ordovician Wufeng Shale from Southeast Chongqing was taken as an example. The PSDCVC model was established using the experimental results including total organic carbon (TOC), carbon element content in organic matter (OM), X-ray diffraction mineral composition analysis and low-pressure N2 adsorption/desorption (LPNA) tests, which were performed on three sets of subsamples. The PSDs associated with OM, clay, other components and shale sample per unit mass were obtained, and the PSDs of the subsamples calculated from PSDCVC method were compared with the results of LPNA and field emission scanning electron microscopy methods to confirm the credibility of PSDCVC results. For the shale samples from the same layer, the pore volumes (PV) of different pore widths associated with OM, clay and other components per unit mass are corresponding constants or similar to these constants, respectively. The PSDs associated with OM, clay and other components are primarily distributed in the pore widths of <5 nm, 20~(-1)00 11111 and 10~(-1)00 nm, respectively. The PVs of pore widths <200 nm contributed by OM, clay and other components per unit mass are 1830.52 x 10~(-4) cm~3/g, 29.52 x 10~(-4) cm3/g and 0.05 x 10~(-4) cm~3/g, respectively. In the shale samples per unit mass, the average PVs of pore widths <200 nm contributed by OM, clay and other components are 49.16 x 10~(-4) cm~3/g, 7.89 x 10~(-4) cm3/g and 0.04 x 10~(-4) cm3/g, representing contributed proportions of 85.80%, 14.14% and 0.06%, respectively. The PVs of pore widths <200 nm in the Wufeng Shale sample with TOC content >0.22% is mainly contributed by OM.
查看更多>>摘要：In oilfield production, it is important to be able to acquire the reservoir status of oil wells in real time, especially for low or ultra-low permeability oil wells. In this paper, based on the reservoir percolation characteristics of the oil layer and combined with the oil well permeability, liquid pressure and oil well pressure formulas, the non-homogeneous linear differential equation for oil well pressure is derived, based on which a submergence depth model of oil well reservoirs is established. The parameter merging is applied to reduce the parameter dimension of the submergence depth model;; this approach substantially reduces the parameter dimension and application complexity and effectively improves the model application range. The model not only conforms to the reservoir percolation law of the oil layer but also applies to the balance laws of other substances with potential energy balancing ability. The application methods studied (namely, the extraction of the greatest common divisor, the weighted dichotomy and least-squares curve fitting) successively reduce the calculation error and expand the application scope. The least-squares curve fitting method causes the submergence depth error to reach the minimum of the 2-norm, and the number of iterations can be accurately assessed by the convergence speed of halving the numerical calculation error in every iteration. This method is suitable not only for the zero submergence depth case in the initial state but also for non-zero submergence depth cases. The experimental results show that the proposed submergence depth model for oil well reservoirs accurately reflects the change laws of submergence depth and time. Combined with the proposed application methods, the corresponding submergence depth can be obtained at any time point. The model and application methods provide strong support for formulating scientific oil production plans and implementing reasonable production methods for oil wells.
查看更多>>摘要：The molecular characteristics of a TOFA/DETA based imidazoline inhibitor were evaluated by analysing the inhibitor protonation profile, the CMC and micelle size and the rate of acid-catalysed hydrolysis of the inhibitor to improve understanding of the corrosion inhibition performance of the main imidazoline component and its hydrolysis products. The ability of the TOFA/DETA imidazoline based corrosion inhibitor and its products of hydrolysis in retarding both uniform and localized corrosion were assessed and compared on wet-ground X65 carbon steel at 80 °C in CO2 saturated 3 wt % NaCl brines. The findings indicate that the imidazoline based inhibitor forms micellar solutions, with a characteristic micelle size of 18 + 9 nm at the CMC (10 ± 1 ppm) in CO2 saturated 3 wt % NaCl brines, and that under such conditions (pH~4.1), the inhibitor is fully protonated which increases inhibitor solubility/dispersibility and enhances molecular adsorption of the positively charged imidazoline on the metal surface thereby improving inhibition performance. Hydrolysis of the imidazoline and amido-amine is acid-catalysed and the consumption of imidazoline follows a pseudo-first-order reaction mechanism with an activation energy of 72.0 + 2.9 kj mol~(-1). The study concludes that the pre-aged inhibitor has different effects on uniform and localized corrosion behavior of X65 carbon steel.
查看更多>>摘要：This study proposes an effcient method to optimize the subsea feld layout with the aim of minimizing the subsea feld development cost, based on the two methods introduced in Part I and Part II for solving the well trajectory planning problem and the location-allocation problem, i.e., 3D Dubins Curve method and Binary Linear Programming (BLP) method, respectively. The most complex part in subsea feld layout optimization is essentially a location-allocation problem of drilling sites embedded with the well trajectory optimization. The full process of our method is clearly summarized in a fowchart. Abundant case studies with comparison to the existing results demonstrate the optimality and the fexibility of our method to solve practical subsea feld layout optimization problems. In the cases studies, we also reveal how different user-defned cost items affect the optimal feld layout. Details of implementing our method for a better performance is also discussed. This work is the third of a series of papers which systematically introduce an effcient method for subsea feld layout optimization to minimize the development cost.
Rodolfo Mauricio Alvarez VelascoLucas Rissi deAndradeNeilton Paixaode Jesus Junior
9页
查看更多>>摘要：Drilling trough salt layers has been a challenge for the oil drilling industry. In this way, water-based muds are a friendly environment, although they tend to dissolve generated salt particles along with the wall of the well. Particularly, the particle dissolution may cause changes in the fluid rheology and physicochemical properties. Other problems related to this are the enlarging of the borehole, the excessive torque, the accumulation of salt gravels in the bottom hole, the well controlling issues, and some other operational situations. Thus, the controlling and prediction of the salt dissolution process in drilling fluids are of great interest. The main objective of this work was to study the dissolution of halite (NaCl) particles in brines at different concentrations on upward flow in tubes that simulate the borehole flow. An experimental apparatus was built, capable of reproducing some drilling conditions as the upward fluid flow where the data of NaCl concentration as function of position and time were obtained. A mass conservation mathematical model based on the continuum mechanic was proposed in order to simulate the process. The model was composed of two differential partial equations generated by the conservation law for the mass of salt in two phases;; a fluid phase of salt dissolved in water and a solid phase of salt particles. The dissolution data were used to estimate the global mass transfer coefficient in different operational conditions and to validate the mathematical model. The total mean deviations were lower than 5 % for the proposed and validated model.
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