Journal of Petroleum Science and Technology
Volume:6 Issue: 2, Autumn 2016

Chang 8 oil deposit, developed in Hohe and Jihe oil fields at the southern Yi-Shan Slop of Ordos Basin, is regarded as a kind of typical sand reservoir formation with super-low porosity, poor permeability, strong anisotropy as well as locally natural faults and fractures. The previous studies believed that matrix reservoir has a good permeability, whereas fracture reservoir has a reverse manner. In the past years, there have been fewer researches on studying matrix-fracture type oil reservoir; therefore, up to now, it has been still difficult to identify whether network hydraulic fracturing can be effectively exploited in low permeable matrix-fracture type reservoir. In this paper, the author tries to analyze the feasibility of network hydraulic fracturing application in Chang 8 oil deposit from aspects such as mineral component, rock brittleness index, and development status of natural fractures, ground stress, and net press during hydraulic fracturing. The statistical results indicate that the geological condition of the research object is confirmed to meet the standard of hydraulic fracturing with a quartz content of about 40.0% to 41.6%, a brittleness index of 42.6% to 54.6%, a high angle or bevel fracture with a fracture density of 0.03 to 2.6 crack per meter, a mean of 0.38 crack per meter of developed natural fracture and horizontal layers, and the difference of two principal horizontal stresses of 2.8 to 5.5 MPa. Therefore, a certain degree of complex fractures can be built by the methods of segmental perforation, interference between multiple clusters, and the increased net pressure. Finally, we concluded that it is an important treatment to effectively develop this type of oil reservoirs by network hydraulic fracture technology in horizontal wells.

In this study, polyvinylidene fluoride (PVDF) ultrafiltration membranes were prepared via immersion precipitation method using a mixture of two solvents triethyl phosphate (TEP) and dimethylacetamide (DMAc), which had different affinities with the nonsolvent (water). Properties of the prepared membranes were characterized using scanning electron microscope (SEM) and contact angle and membrane porosity measurements. The prepared membranes were further investigated in terms of pure water flux and BSA rejection in cross flow filtration experiments. The results showed that by using a mixture of DMAc and TEP as solvent and changing the mixed solvent composition, membranes with different morphologies from sponge-like to macrovoid containing were obtained.
Maximum flux of the prepared membranes with different solvent mixing ratios was obtained for the one with 60%wt TEP in the casting solution of PVDF/TEP-DMAc/ PEG which equals to 76.8 lm-2h-1. The effect of addition of polyethylene glycol with different molecular weight on morphology and performance of the membranes has also been discussed.

The buckling behavior of rod strings in wellbore is one of the key issues in petroleum engineering. The slender rod strings in vertical wellbore were selected as research objects. Based on the energy method, the critical load formulas of sinusoidal and helical buckling were derived for the string with the bottom of the wellbore pressure. According to the sinusoidal and helical buckling’s geometry of the pressurized column, the contact friction state of post-buckling between the rod strings and the wellbore was considered. This paper adopted Lagrange multiplier method to describe sliding displacement boundary conditions of wellbore and introduced gravitational potential energy and friction resistance dissipated energy in the energy method. The contact forces and friction resistances between the rod string and wellbore were derived in vertical wells. The post buckling experimental apparatus was also developed in this paper. The sinusoidal and helical buckling critical loads and friction resistances were derived under different loads. The experimental results are consistent with the theoretical results. Therefore, this article would provide an effective method for buckling column such as drilling and coiled tubing.

Membrane-based pervaporation (PV) has attracted much attention in the dehydration of organic solvents. Permeate pressure and feed flow rate are two important parameters, which affect membrane performance in pervaporation. The effects of these two parameters on the performance of a commercial poly (vinyl alcohol) membrane in the dehydration of benzene have been investigated in this work. The experiments have been carried out at a constant temperature of 60°C, and pressure and feed flow rate range from 1 to 20 mmHg and from 200 to 1200 ml/min respectively. The results indicate that variations in vacuum, especially in permeate pressures of less than 10 mmHg, greatly affect flux and selectivity so that water flux and separation factor increase from 0.98 to 2.63 (gr/hm2) and from 160 to 310 respectively by decreasing permeate pressure from 10 to 1 mmHg. Furthermore, increasing flow rate improves membrane performance only at rates of below 1000 ml/min, and no changes are observed at higher feed flow rates.

In this paper, we detail our results for the impact of MWCNT on the thermal and rheological properties of oil-based drilling muds. Our analysis considers the effects of time, temperature, and MWCNT volume fraction. The scanning electron microscopy imaging technique was used to monitor the MWCNTsdispersion quality. The experimental results unveil a considerable enhancement in the thermal conductivity of the MWCNT-oil-based mud by 40.3% (and 43.1% in case of functionalized MWCNT) and 1% vol. MWCNT. The rheological properties results for the MWCNT-oil-based mud exhibit a similar (improvement) trend by reducing annular viscosity and increasing yield point and gel strength. The high-temperature high-pressure filtration tests conducted at 280°F and 500 psi show a reduction of 16.67% for the filtrate amount in case of MWCNT-oil-based mud (with 1% vol. MWCNT). The effect of time on thermal conductivity reduction in both unfunctionalized and functionalized systems was observed to equalize (at 9.7%), after 100 hours of sample preparation. The performance results of MWCNT-oil-based mud are presented for an actual industrial drilling operation case.

A series of experiments on the synthesis of poly (ethylene terephthalate) (PET)/organo-montmorillonite (MMT) nanocomposites were carried out in a pressurized reactor using alkyl ammonium exchanged smectite clays, (Closite 30B).Given the degradation of organoclay at high temperatures, the in situ polymerization process was carried out at mild temperatures ranging from 210 to 230°C for 40 minutes followed by solid state polymerization (SSP) at 245°C for 30 minutes at a pressure of 5 mbar. The nanocomposites were prepared using different weight percentages (1-5)of organoclay. The reaction completed when the mixing torque ceased to change as recorded by the auto data acquisition system of the pressure reactor. The DSC analysis provided information on the course of the thermal characterization of the PET nanocomposites versus regular PET. As shown by the results of DSC cooling scan, all the PET nanocomposite samples have higher crystallization temperatures (Tc) and faster crystallization rates (∆HC/t) compared to regular PET. Furthermore, the opposite behavior is observed for t1/2. This is due to the fact that the nucleation of organoclay nanoparticles reduces the crystallite size in the PET nanocomposites. The XRD results indicated that the peaks in the 2θ angle from 1° to 7° were disappeared, which is an indication of an exfoliated MMT.In addition, The atomic force microscope (AFM) results showed broken mirror like lamellae, confirming the exfoliated results of the XRD analysis. The peaks are indexed according to the 2θ angle from 10° to 30° known assignments of the triclinic unit cell dimensions for PET. The comparative crystallite size of the PET nanocomposites samples (1-5%wt organoclay) can be deduced from the peak ratio change of 2θ angle from 10° to 30°. Heat distortion (or deflection) temperature (HDT) was enhanced by increasing the amount of organoclay in PET nanocomposites compared to regular PET. The tensile test results of 2%wt organoclay show an increase of 58% in the tensile strength of this sample. As a result of MMT agglomeration, due to the high temperature instability of Closite 30B, the relative oxygen pressure drop data shows fluctuations. However, as an overall trend, PET nanocomposite gives about 50% greater reduction in O2 pressure drop or relative oxygen permeability compared with a homo structure.

Facies modeling is an essential part of reservoir characterization. The connectivity of facies model is very critical for the dynamic modeling of reservoirs. Carbonate reservoirs are so heterogeneous that variogram-based methods like sequential indicator simulation are not very useful for facies modeling. In this paper, multiple point geostatistics (MPS) is used for facies modeling in one of the oil fields in the southwest of Iran. MPS uses spatial correlation of multiple points at the same time to characterize the relationships between the facies. A small part of the oil field, in the vicinity of the simulation grid, is used as a training image, in which there is 25 well data for creating suitable training image by the principal component analysis (PCA) method. In this study, MPS is successfully applied to facies modeling and the spatial continuity of facies is reasonably reproduced. The facies model verifies the reproduction of facies proportion in training image and wells. Also, five wells are used for the cross correlation of the facies model. The results indicate that the facies model shows a strong correlation with the facies of these five wells. Additional hard data, which is extracted from high confidence seismic data, is so useful for the improvement of the facies model.

Dimerization process is essential for producing copolymers. The features of dimerization process like thermal-oxidative degradation should be well known to reach maximum efficiency and a superior reactor design. Also, the degradation mechanism of biodegradable polymers is important during sterilization processes. Thermal-oxidative degradation of PGA, PLLA, and their binary copolymers was investigated under isothermal heating as well as dynamic heating. All the samples were prepared by a polycondensation process and were characterized by TG, DTG, DSC, and HNMR analyses. Activation energy under dynamic heating was obtained by using Friedman plot. A new three stage mechanism, namely random, transition, and specific stages is proposed for dynamic heating degradation. Isothermal heating investigation is conducted under an inert atmosphere, and frequency factor and activation energy were achieved. It was found that the activation energy under isothermal heating is generally higher than that under dynamic heating. It was found that the rate of degradation increases significantly with an increase in temperature. The effects of pressure on the degradation rate were studied in different atmospheres with various oxygen partial pressures. Pressure effect was correlated by a second order polynomial in terms of total pressure. The obtained activation energies under isothermal heating were in good agreement with those reported by others. The complete kinetic scheme suitable for reactor design for the thermal-oxidative degradation of the samples was reported. Finally, the optimal operational conditions for the dimerization process were reported.

Turbine oil plays an important role in supporting optimal steam turbine performance. Some additives in turbine oil can cause emulsification when the oil is contaminated by water, so demulsibility is a very important property of the steam turbine oil. In order to improve the demulsibility of steam turbine oil, two kinds of polyether-silicone comb copolymers are synthesized and used as steam turbine oil demulsifiers. The polyether-silicone copolymers present better demulsibility properties than the demulsifiers on the market at the present time. The influences of demulsifiers on turbine oil-water interfacial tension and demulsibility time were measured. All the demulsifiers obviously decrease interfacial tension andsimultaneously reduced the demulsibility time. The variation tendency of interfacial tension and demulsibility time is basically consistent. The oil-water interfacial elastic modulus and viscous modulus were also measured as a function of strain and frequency respectively. The results showed that the demulsifiers decrease the oil-water interfacial elastic modulus, which was favorable to the demulsification.

The use of elastomer additives to solve the problems in oil well cementing has been investigated in recent years by several research groups in the petroleum industry. This study includes the laboratory examination of the effect of elastomer additives on the physical properties of heavy-weight oil well cement. In the research process, a candidate well is selected and the properties of the cement slurry used in a problematic section of the well are tested in the laboratory. Then, elastomer additives are added as an elastic agent and the improvements in the cement slurry and stone properties are studied. This article discusses the problems associated with the conventional heavy-weight oil well cement used in the candidate well and reports the detail of the improvements in cement properties obtained by adding an elastomer additive to the cement slurry formulation as an elastic agent. These properties include cement slurry rheological properties, free water, fluid loss, thickening time, cement stone elasticity properties, and compressive strength. The elastomer additive increases the yield point and plastic viscosity, but it decreases the free water and fluid loss of cement slurry. In addition, the cement stone compressive strength decreases; however, there is an optimum concentration of the elastomer additive at which the maximum compressive strength is reached. Moreover, the elasticity properties of the cement stone are improved and a lower value for the Young’s modulus and a higher value for the Poisson’s ratio are achieved. The theories supporting the results are discussed in the discussion section. The results of this study can be used to optimize the cement slurry design in any given set of conditions.

Two late transition metal catalysts based on 2,6-bis(imino)pyridine iron(II) were synthesized by introducing methyl substitution (catalyst A) and t-Butyl substitution (catalyst B) at the ortho position of the aryl rings of the ligand. Comparative ethylene polymerizations using the catalysts showed quiet different behaviors. The activity of catalyst A was higher than that of catalyst B in all of the polymerization conditions used. The highest activities of these catalysts were obtained at almost 25°C. Activities of the catalysts increased with increasing both monomer pressure and [Al]: [Fe] molar ratio. Multi modal peaks were appeared in the DSC analysis of oligomers obtained by catalyst A, while in the DSC analysis of the polymer obtained using catalyst B unimodal peaks were appeared. It is suggested that catalyst A containing less bulkier substitution produced polymer with different molecular weight fractions and different melting points. Besides, the t-butyl group in catalyst B resulted in producing polyethylene (PE) with single sharp DSC peaks; the latter is due to the formation of highly linear polyethylene. Polymerization temperatures affected the pattern of DSC thermograms in terms of number and shape of the peaks of the obtained polymers by catalyst A. Catalyst A produced linear oligomers contained liner olefinic part with a number average molecular weight in the range of 260 to 361.

The oxidation and degradation of hydrocarbons at high temperature and pressure in the presence of oxygen is one of the common oil product problems. There are many antioxidants to prevent or inhibit oxidation processes; molybdenum and zinc dithiocarbamates are known as powerful antioxidants. In this paper, the oxidation inhibition time of cumene has been investigated using zinc and molybdenum dithiocarbamate substituted with different alkyl groups as antioxidants and azobisisobutyronitrile (AIBN) as the initiator. The best result obtained for molybdenum dibutyldithiocarbamate was about 210 min, while zinc dialkyldithiophosphate (ZDDP), a well known commercial antioxidant, showed an oxidation inhibition time of about 14 min under the same conditions. It was shown that antioxidancy properties decreased with increasing the chain length of the substituted alkyl groups. This can be explained by the fact that alkyl groups participate in the oxidation process and thus increasing the alkyl chain length reduces antioxidancy effect. The synergism effect of molybdenum dibenzyl dithiocarbamate on ZDDP was also investigated and the oxidation inhibition time of about 110 min was obtained, which was greater than that of any individual antioxidant.