AbstractMixed organic and mineral deposits clogging perforations in the near wellbore area is a significant problem in the oil and gas industry. Matrix acidizing is widely applied to relieve this damage in the Haoud Berkaoui region using three different acid systems proposed by company services to restore the initial properties. This work aims to understand and interpret the history to investigate the efficient acid system adapted to the reservoir of two candidate wells. Different data are collected and analyzed. However, laboratory tests were conducted to verify the performance of each acid. Matching laboratory results, Acid Response Curves (ARC) interpretation, and microscopic photos with field data analysis show that only one mud acid system (6% HCl-1.5% HF) among the three is adequately used in the field to minimize the skin factor. It also increases the relative permeability in the wellbore region (7 for well N1 and 3.7 for well N2) and a flow rate gain (0.25 m3/h for the well N2). This study allows the best acid selection and suitable additives for maximum oil recovery of wells, solving problems associated with the production of wells and decreasing the cost of the operation in the future.

AbstractMost of the oil fields in China have entered the stage of high-water-content development, which has become the primary means to improve the recovery rate of high-water-content oil fields by changing the injection agent. MDFFA membrane oil drive technology is a new type of tertiary oil recovery technology that uses an aqueous solution as the transfer medium; however, it is rarely applied in the field of tight oil reservoirs in China. In this study, molecular film-wall microgravity and water-wall microgravity were compared for tight reservoirs in the Shengli oilfield. It was concluded that the MDFFA dominates in competitive adsorption, breaks through and removes the hydrated layer, and finally adsorbs firmly on the pore wall to form a nanoscale ultrathin film. The application conditions of the MDFFA were also explored, and its wetting angle was tested. Further, the variation law of MDFFA adsorption was studied, and the mechanism of MDFFA drag reduction was explained in terms of reducing the boundary layer effect and water injection friction resistance. The natural cores procured from the Shengli tight oil field were analyzed for MDFFA membrane drive cores, and a reasonable injection concentration was selected. Through a series of mechanistic and experimental studies, we provided theoretical and technical references for the development of increased tight oil production.

AbstractThe work deals with the study of the effect of the process of heavy oil etherification on the aggregative stability of asphaltenes and their structural changes. The etherification was carried out at various temperatures from 25 to 100 °C for 8 h. It has been found that with an increasing temperature of oil treatment with isopropyl alcohol, an increase in the yield of resins and asphaltenes by 4 wt% is observed. Based on the data of IR-spectroscopy and NMR, it has been found that isopropyl radicals were likely to be incorporated into asphaltenes. In the structure of asphaltenes, aliphaticity, and branching increase by 3.5 and 2.9 times compared to the initial asphaltenes, respectively. Structural and group characteristics of asphaltenes were changed after the oil etherification, which was especially evident after the 100 °C of process temperature. It was also found that the treatment of heavy oil with isopropyl alcohol practically does not affect the stability of asphaltenes.

AbstractThe development of marine gas hydrate from low-permeability offshore reservoirs with serious sand incursion issues is a challenging task. Currently, there are no mature technologies in the world. Therefore, we proposed a comprehensive development process, including the following measures: (1) Vertical injection-production well pattern enhanced by multi-layer fracturing and hot water injection by seawater source heat pump. (2) An advanced multi-layer hydraulic fracturing technique incorporating cold fracturing fluid, low-temperature consolidation proppant, multi-stage sliding sleeve packer, and a chemical diverting agent. (3) A series of sand control measures including hydraulic fracturing, consolidation proppant, and stand-alone screen. (4) Several rounds of hot water injection-soaking-production (huff-n-puff) on injection wells, and finally continuous injection-production, with depressurization. Then, we built a gas hydrate decomposition rate model to simulate this process. The results show that hot water injection combined with multi-layer hydraulic fracturing can significantly improve the gas hydrate dissociation rate compared with the schemes without hot water injection or fracturing. Combining hot water injection by seawater source heat pump, multi-layer horizontal fractures by advanced hydraulic fracturing technique, and a set of sand control techniques, can efficiently control sand while producing gas hydrate.

AbstractThe oil or petroleum industry is among the most significant world industries and plays a decisive role in economic and political interactions due to its strategic importance. This massive industry has significantly been influenced by instabilities, political unrests, and sudden price fluctuation in recent years. Additionally, the decision-making process in the oil SC has become a challenging issue because of the presence of considerable facilities in the oil fields, oil refining, and distribution of petroleum products. Hence, the integrated optimization of oil SC has been quite popular with researchers. On the other hand, since there are environmental requirements, people have their shares in the extension of this industry, and developmental planning should consider ecological and social issues. The effort has been made in this article to propose a mathematical programming model for the design of oil supply chain network to reduce their environmental effects and improve the social indices while saving costs. Then, the model was solved with actual data from a real case study of the Iran Oil Industry. Finally, some recommendations have been provided based on analyses of the numerical results.

AbstractReservoir water sensitivity damage means that the contact between the external fluid and reservoir rock lead to the hydration, expansion, dispersion, and migration of clay minerals, thereby reducing the formation permeability and causing damage to the reservoir. In this study, the transformation of smectite to illite (S-I) is promoted by endogenous microorganisms to achieve anti-swelling of the clay minerals and reduce the water sensitivity damage of the reservoir. The microbial community reducing Fe(III) was enriched from the samples of Karamay Oilfield, Xinjiang, and microbial community diversity was analyzed by the 16S rRNA gene sequencing. The Fe(II) ion concentration in the interaction medium was monitored, and the maximum iron reduction rates reached 60.2%. The structural changes of smectite before and after microbial treatment were observed by Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy. The result demonstrated that the reduction of Fe(III) was accompanied by the transformation of S-I. There may be some endogenous microorganisms that transform S-I in low permeability reservoirs. This study is of great significance for oilfields to realize clay mineral anti-swelling and eliminate reservoir water sensitivity damage by endogenous microorganisms.

AbstractThe induced hydraulic fracturing in reservoirs is the result of interactions between a fluid-driven pressure increase in the reservoir and different lithology. To investigate the fracture height containment in a transitional shale formation, a three-layer medium fracturing model with the shale layer being used as an injection layer was first established. Then, based on the logging lithology, the propagation behavior of hydraulic fractures under real lithological sedimentary sequences was investigated. The results show that the hydraulic fracture can either cross through the lithological interface, be arrested by the interface, or stopped at the adjacent layer after crossing through the interface. Some specific properties of different lithologies may contain fracture height, such as sandstone with high tensile strength, coal with low stiffness, as well as clay shale with very low permeability. In the real lithological sedimentary sequence, hydraulic fractures are often blocked at the interface between a sandstone-shale combination or stop at the shale layer after crossing through the interface, and even increasing the injection rate cannot change this situation. The research results have of great significance for optimizing the trajectory of horizontal wells and fracturing operation parameters in reservoirs with frequent interbedded lithology.

AbstractSteelwork is one of the main emitters of CO2 in the world. For this reason, many efforts are being made to reduce or avoid CO2 emissions by unit optimization or by carbon capture and storage (CCS) or utilization (CCU) processes. In the steelwork, three main off-gases are generated including the Blast Furnace Gas (BFG), the Coke-Oven Gas (COG), and the Basic Oxygen Furnace Gas (BOFG). Different processes and technologies can be proposed for recovery based on the volume and composition of the steelwork off-gases. In this paper, the BFG stream is utilized to improve the efficiency of the GTL process and reduce CO2 emissions. For this purpose, a part of the BFG gases is mixed with the syngas produced in the methane autothermal reforming process and injected into the Fischer-Tropsch reactor to produce liquid hydrocarbons. The BFG flow rate was determined according to the optimum H2/CO value. The pressure and volume of the reactor were set at 10 bar and 300 m3 for optimal hydrocarbon production. The simulation results showed that mixing a portion of the BFG with the syngas increases the C5+ production by 11268 bbl/day, while the CO2 emissions decreased by 146529 ton/yr.

AbstractHigh-content rubber modified asphalt would let out lots of volatile organic compounds (VOCs), bio-oil was used to reduce the VOCs emission and mixing temperature of high-content rubber modified asphalt. The molecular model of high-content rubber modified bio-asphalt (HRMBA) was built to calculate the solubility parameter, free volume, molecular orientation, and radial distribution function. The effects of bio-oil on the physicochemical properties of HRMBA during VOCs emission process were studied deeply using molecular dynamic simulations and first principles. The differential scanning calorimeter (DSC), Fourier infrared spectrometer (FT-IR), and gel chromatography (GPC) were used to test the glass transition temperature, functional groups, and molecular aggregate and verify the simulated results. The results show that the optimum contents of waste tire in HRMBA is 35%, and bio-oil can promote the compatibility between rubber and asphalt. Free volume of HRMBA shows a strong correlation with the probe Connolly radius, and Connolly radius increases the molecular movements and dissolution of HRMBA. Moreover, the compatibility between bio-oil and rubber are good. Bio-oil can improve the dissolution of rubber into asphalt and inhibit the VOCs emissions of HRMBA. The compatibility between rubber and asphalt are damaged after VOCs emission. A new calculation method was used to evaluate the physicochemical properties of HRMBA, and experiment methods were also used to verify these.

AbstractCarter’s model of fluid loss is used in the oil and gas industry performing the numerical approach of leak-off. Its deduction applies some simplifying assumptions, such as the difference between fluid pressure and constant pore pressure and filtration process approximation to a unidirectional flow, perpendicular to the fracture plane. For this paper, the so-called Chimas is an hydromechanical simulator of oil reservoirs, fully coupled and implicit, in a way that considers the poroelastic effects on the propagation of fractures. The leak-off process is explicitly treated in the fracture boundary conditions using Darcy’s law. The objective of this work is to validate the filtration phenomenon of Chimas hydromechanical simulator comparing the parameters of length, width and injection pressure with those obtained using an iterative method implemented in MatLab and which includes Carter’s analytical equation. Numerical accuracy was validated against asymptotic analytical solutions. The agreement between the iterative method and the analytical solutions was particularly good in relation the length fracture and injection pressure.

AbstractEstimating production profile from temperature data is of great significance for production increase and cost reduction in well production process. This study aims to provide a cost-effective direct method of interpreting flow profiles from temperature measurements. The concept of representative inspired by randomized distribution regarding heat conduction representative points for each no-influx section is proposed. Three assumptions regarding existence, distribution and independence of representatives are introduced to establish a copula-based statistical method of converting fitted distributions of representative, to distributions of relaxation distances for each no-influx section, and then to estimate the production profile. The method is applied on a horizontal gas well on the east slope of western Sichuan depression, and the simulated results are compared with the production logging data. The error of estimators for each no-influx section is between 6.7% and 11.8%, which is satisfactory. Sensitivity analyses are conducted regarding temperature measurement error, and the results verify the robustness of this method. This paper provides a reliable solution to interpret production profile from relatively inaccurate temperature data when the perforation zones are adjacently close. The findings of this study can help for better understanding of low-cost production allocation and uncertain flow state modeling problems.

AbstractUse of the synergistic effect between nanomaterials and ionic liquids is of great significance for designing high-performance lubricating materials. In this work, Zn-MOF/[P88814]DEHP (zinc complexes with 2-aminoterephthalic acid nanosheets/trioctyltetradecylphosphonium bis (2-ethylhexyl) phosphate) composites were successfully synthesized by grinding the mixture of [P88814]DEHP and Zn-MOF with different mass ratios and evaluated as a new kind of the white oil additive using a four-ball testing machine. Results demonstrate that the optimal mass ratio of Zn-MOF to [P88814]DEHP was 1:1 and the Zn-MOF/[P88814]DEHP composite with 2.0 wt% addition amount into the white oil significantly reduced friction coefficient and wear. Such obvious friction-reducing and outstanding anti-wear properties of Zn-MOF/[P88814]DEHP composite could be attributed to the synergistic lubrication between Zn-MOF and [P88814]DEHP. This work investigated the synergistic lubrication between MOFs and ILs, which provided a new idea for designing and preparing new lubricating oil additives.

AbstractAn experimental campaign is conducted to investigate the pressure drop during the restart of a heavy oil-water core-annular flow (CAF) from a stratified configuration in a polyvinyl chloride (PVC) horizontal pipe. The evolution characteristic of restart pressure drop along time is explored, and the effects of various factors including oil holdup (0.26-0.76), oil viscosity (1.0553-3.02 Pa·s), standstill period (0.5 & 1.0 h) and water cleaning superficial velocity (0.25-1.01 m/s) on maximum restart pressure drop are emphatically investigated. The results demonstrate that the restart process can be divided into decay and steady two stages. The maximum restart pressure drop generally increases along with the increase of oil holdup, oil viscosity, standstill period and water cleaning superficial velocity. Moreover, of all the measured variables, oil holdup and water cleaning superficial velocity have a significant influence on maximum restart pressure drop. The results obtained can provide a theoretical reference and practical guidance for the development of appropriate restart schemes for on-site shutdown pipelines.

AbstractTo solve the problem that indiscriminate subsidy policy is difficult to effectively exert an incentive effect on the investment behavior of enterprises, this paper puts forward a type of differentiated subsidy considering resource conditions, which consists of a basic security subsidy and a variable excitation subsidy. First, on the premise of guaranteeing the basic rate of return of enterprises, the net present value formula is used to compute the basic allowance. Then, according to the principal-agent theory, the revenue functions of government and enterprises are constructed, and the calculation model of the incentive scheme can be obtained by quantifying the correlation coefficients between resource conditions and social benefits. The case application shows that the Fuling block requires a significantly smaller amount of subsidy than the Weiyuan block due to its superior resources and development conditions, which verifies the necessity of considering regional differences in the design of shale gas development subsidies. This differentiated subsidy model can improve the efficiency of the use of financial funds while taking into account the fairness of policy implementation in different regions.

AbstractNew approaches to low salinity water (LSW) injection methods, such as LSW/surfactant, LSW/polymer, and LSW/nanofluid flooding, have been studied for oil reservoirs. Numerous researchers discussed the mechanisms related to enhanced oil recovery (EOR) efficiency and highlighted the significant impact of the wettability alteration and interfacial tension (IFT) reduction. This work studied the effect of exposure time on the wettability alteration and IFT in the LSW/nanoparticle (LSWN) flooding. Contact angle tests investigated rock wettability over a series of different times. A pendant drop tensiometer was used to measure the IFT. By coreflood apparatus, waterflood tests were also conducted, considering the effect of soaking time. Laboratory results showed that the involved mechanisms are time-dependent. More water-wet conditions and higher oil recovery were obtained under longer soaking time. In addition, the positive effect of LSWN was observed in tertiary flooding tests. The results also indicate that the effect of water-soluble oil compounds should be considered in measuring wettability and IFT.

AbstractAfter several years of gas production, a black solid hydrocarbon material began to be produced along with the gas stream from the Risha gas field, in the northeastern part of Jordan. The main reason for the formation of this material is still unknown until this time, so knowing the source of this material is this study’s main goal. Organic geochemical studies for black solid material and effective source rocks (Lower Silurian shales) are used to determine the physical and organic components of the produced black solid material (heavy oil) and attempt to identify its source. The black solid material demonstrates high organic carbon (TOC = 12% by leco instrument) and a high calorific value, like those of oils, asphalts, and shale oils with moderate sulfur content. The gross composition of the black solid material sample is dominated by saturates and asphaltene but contains very low aromatic hydrocarbons reflecting the naphthenic oil type. Meanwhile, the Silurian extracts range between paraffinic and paraffinic-naphthenic organic matters. The biomarker indicators related depositional environment and carbon isotopic composition for the black solid material sample and Silurian extracts, show that they were relatively deposited in a reducing marine environment. The black material reveals lower maturity level than the Silurian extracts. Oil/source rock correlation study for the studied samples suggests strong affinity between the black material and Lower Silurian source rock in their source characteristics, suggesting that the black hydrocarbon material was expelled from the Silurian source rocks at low maturity stage as normal oil. This normal oil is subjected to secondary alteration process (evaporative fractionation) and was stored in the reservoir. It contaminated with some inorganic material that was introduced into the well as a component of a drilling mud additive or drill string lubricant or, potentially, in part, a corrosion product of wellbore tubulars, since significant iron was present in the sample.

AbstractPolyoxyalkylenes are widely studied as clay swelling inhibitors. Although many additives are available, the operations require more efficient formulations. This work synthesized and characterized two of molecules: poly(ethylene glycol)(PEG) modified with hydrocarbon chains of different lengths; and poly(amidoamine) dendrimers(PAMAM) and PEG-modified PAMAM. The clay swelling inhibition efficiency was evaluated by the Foster swelling test. For the hydrophobized PEG derivatives, there is an optimum hydrocarbon chain size (C6-C10) to achieve the best performance. The best result was obtained for PEG-modified PAMAM(1:1), tested for the first time, being its performance even better than a commercial additive widely used in the petroleum industry.

AbstractOil flow in a circular piping usually requires excessive modeling with detailed correlations to describe the oil flow behavior. The ineffective pour point depressants and the inefficient heat tracing makes oil flow simulation an essential task. Due to the varying of oil characteristics, a robust modeling approach is necessary to guarantee the integrity of the oil flow in the piping system and to avoid additional costs. In this work, a proposed approach coordinates the modeling tools (e.g. Aspen HYSYS®, COMSOL Multiphysics®) to simulate the oil flow in a circular pipe satisfactorily. The oil properties have been extracted from Aspen HYSYS® and used in COMSOL Multiphysics® to describe the varying in oil flow characteristics. Numerous computational trials have been conducted to estimate the oil temperature profiles in the axial and radial directions to ensure the oil flow above the pour point. Moreover, the numerical results were computed to estimate the oil temperature profiles for constant and temperature-dependent oil properties. Finally, an analytical approach was established using dimensional analysis to compare with COMSOL numerical results at constant oil properties. Both results showed a consistent trend match.

AbstractWax/asphaltene deposition has been an important problem in the gas condensate reservoirs development. The cold plate device is designed to reveal the effect of operating conditions on the wax/asphaltene deposition behavior. The characteristic of wax/asphaltene deposition with well conditions is determined. The results show that when the temperature difference was considered, the growth rate of wax deposition thickness in the operation period was that stabilizing first, rising again, and then slowing down. However, the temperature and hydrogen bonding interaction significantly affects the asphaltene deposition process. The asphaltene deposition rate was stable at the beginning period of operation, then increased significantly, and decreased gradually after reaching the peak value of 21.61 g/cm2·h. An identification diagram of the wellbore deposition location is established. Increased deposition surface area of the cold plate structural design ensures qualitative and quantitative characterization of wax/asphaltene deposition traits. The real well fluids components were employed in the experiments to obtain critical conditions for wax/asphaltene deposition which approximated actual production conditions. This diagram facilitates the reliable identification of wax/asphaltene removal areas in the wellbore during production. This study provides a comprehensive understanding of the wax/asphaltene deposition behavior, which helps the gas condensate well operation safety and efficiency.

AbstractThis paper presents an integrated facies, diagenesis, and sequence stratigraphic analysis, and reservoir quality evaluation of the siliciclastic hydrocarbon reservoirs (Ghar Member of the Asmari Formation) in the NW Persian Gulf. Results of core descriptions, thin sections petrography, X-ray computed tomography (CT) scanning, X-ray diffraction, sieve analysis, porosity–permeability measurements, and petrophysical logs are used. Four petrofacies are recognized indicating deposition in shore-line (beach) sand bodies and supratidal to intertidal sub-environments. Calcite and anhydrite cementation, dolomitization, recrystallization, compaction, and fracturing are diagenetic processes which occurred in marine, hypersaline, and shallow burial realms. A large-scale transgressive–regressive sequence and five deepening-upward cycles are defined. Hydraulic flow units and pore-size classes are defined. The best reservoir units (hydraulic units 5 to 8 and pore-size classes 4 and 5) are formed within the well-sorted, rounded, and mature sand/sandstone facies in which intergranular pores are predominant and diagenetic imprints are negligible. These facies are located in lower-half of depositional cycles. Carbonate-dominated facies show variable reservoir properties depending on their diagenetic alterations. In these facies, dolomitization and fracturing improved the permeability. This study shows that reservoir properties of the Ghar Member are strongly facies-controlled and, therefore, are easily predictable within a sequence stratigraphic framework.