Petroleum Research最新文献

Well productivity in the Asmari carbonate formation of southwest Iran has decreased in recent years as a result of production issues. The production rate must be maintained below 1500 STB/day to prevent water coning. In this study, a gas lift well is modeled using data from one of the producing wells of this field. Nodal analysis is performed using lift-gas injection rates and wellhead pressures at different reservoir pressures and water cut conditions to optimize production. Economic aspects are considered to optimize the artificial gas injection rates at different tubing head pressures and water cut conditions. Increasing the lift-gas injection rate from 0.4 MMscf/day to 1 MMscf/day enhances the oil production rate by 37.71% and 43.89% for 10% and 30% water cut conditions, respectively. Gas injection rates of 5.2 MMscf/day and 5.4 MMscf/day are determined to be economically optimal for 30% water cut with tubing head pressures of 260 psig and 270 psig, respectively.

Foam flooding using CO₂ has emerged as a promising method for both enhanced oil recovery (EOR) and the storage of CO₂ in geological reservoirs. This study conducts a thorough analysis of the behavior of CO₂ and N₂ foams in bulk and porous media, utilizing bubble-scale analyses and foam flooding experiments. The study compares the foamability and longevity of CO₂ and N₂ foams, with findings indicating that N₂ foam bubbles tend to be smaller and less varied in size than CO₂ foam bubbles, leading to increased foam stability. Additionally, the study compares the half-lives of CO₂ and N₂ foams generated through sparging and winding methods, showing that N₂ foam has half-lives 22 and 10 times greater than CO₂ foam when produced using the sparging and winding methods, respectively. Furthermore, CO₂ foam generated through the sparging method had a lower foaming volume than N₂ foam due to CO₂'s solubility. In the foam flooding experiments, N₂ foam proved more effective in recovering oil from porous media than CO₂ foam, thus demonstrating the effectiveness of the foam injection procedure. These results offer valuable insights into the differing performance of N₂ and CO₂ foam floods for EOR and CO₂ geological storage.

During the life of a well, treatments are carried out to boost productivity by stimulating initially unproduced zones. These treatments include hydraulic fracturing, matrix acidization, and acid fracturing, among others. Hydraulic fracturing treatment is generally applied to deeper reservoirs of oil or natural gas for enhanced recovery. By infusing proppant, water, and chemicals under extreme pressure during the fracturing procedure, fissures in and beneath the reservoir layer can be accessed and expanded. Another stimulating procedure, matrix acidization, involves injecting acid down the drilling hole to permeate the rock fissures at stresses lower than the fracture stress. In addition, carbonate reservoir acid fracturing stimulation is commonly used as an acid treatment technique whereby a pressure greater than the formation disintegration pressure or spontaneous fracture closure pressure is used to compress acid into the reservoir. These treatments allow existing wells to sustain hydrocarbon production without new wells being drilled. Diverters, when employed efficiently, can prevent the need to use a rig to provide momentary physical barriers, thus lowering the cost of the workover. Recent improvements in diversion technology make use of a variety of degradable particles that act as momentary bridges, either at the perforation entries or inside the existing fractures. The aim of this study is to introduce different types of mechanical and chemical diverters used to enhance the productivity of wells. This study explains the concepts of different types of diverters and their applications in several formations, it will also help readers to understand the selection procedures based on the suitability and requirements of diverter use by case studies from around the world.

Waxy crude oil is known for its high wax contents that can potentially result in gelling following sufficient cooling of the transportation line in the subsea bed at offshore fields. The gelling over the entire lines requires an accurately predicted restart pressure to restart the clogged and idle system. However, the common way of predicting the restart pressure has been reported to result in over-designed and predicted piping parameters. Recent research findings evidenced the formation of voids which would reduce the restart pressure significantly. The study conducted in this paper is aimed at investigating the voids size distribution in gelled crude oil across and along transportation pipelines. Sets of experiments simulating crude oil transportation during both static and dynamic cooling were conducted. The gelled crude oil below the pour point temperature was then scanned using a Magnetic Resonance Imaging (MRI) system to detect the voids formed. The resulting voids at each scanning cross-section were quantified, and their distributions were investigated. It was observed that dynamic cooling had minimal impacts on the voids size difference along the pipeline with the difference in voids areas within 10 mm² to be twice and uniform for the entire flow rates tested. However, voids size in statically cooled waxy crude oil was found to be highly distributed with a maximum of 6 voids size distribution in 10 mm² ranges. The low-end temperature had the highest size difference while the difference was decreasing with higher end temperatures. This study shows that the voids amount in dynamically cooled waxy crude oil could also be estimated with lower numbers of cross-sectional voids areas. However, the higher cross-sectional voids detection is recommended while estimating voids in statically cooled waxy crude oil.

In this study, the employment of mud-pulse generators to improve the efficiency of wellbores under complex mining and geological conditions is examined. A systemic analysis is made of the primary theoretical basis of the study. The benefits of a mud-pulse generator (a high-impulse hydraulic hammer) for wellbore production are stated based on the presented theoretical basis. The results not only show the benefits of mud-pulse generator employment but also provide an analysis of methods that can be used to improve the high-impulse hydraulic hammer efficiency. The acquired results have a substantial practical value not only for specialists, who research, develop, and manage wellbore operations, but also for engineers, who improve the process and modernize existing wellbores, and other experts in the field of wellbore production.

Lucaogou Formation in the Santanghu Basin is a special lacustrine fine-grained sedimentary deposits rich in volcanic debris and carbonate, with abundant shale oil resources. However, understanding of shale oil characteristics and genesis remains unclear. Lithofacies, sedimentary environment, and formation mechanisms of tuffaceous shale oil are investigated based on core and thin section observations, X-ray diffraction, field emission SEM and geochemical analysis. Results show that three mixed lithofacies types are developed in Lucaogou Formation: blocky tuff, laminated tuffaceous dolomite, and laminated dolomitic tuff. These lithofacies types are characterized by high content of felsic and dolostone, widespread organic matter, and low clay content. Formation of tuffaceous shale oil sweet spots is primarily influenced by four factors: inputting of volcanic ash as a high-quality source rocks and reservoirs provides good material basis; devitrification of volcanic glass, calcitization, and dissolution are crucial for formation of reservoirs; expulsion of source rocks with high-abundance organic matter expulsion facilitates migration and accumulation of hydrocarbon in adjacent reservoirs; fracture development improves reservoir permeability to form highly productive sweet spots. By analyzing characteristics and genesis of tuffaceous shale oil, the main controlling factors of reservoir physical property and oil saturation are clarified, which is of great significance for selection of shale oil exploration zones.

The asphaltene fractions of the bitumens of Eastern Dahomey Basin in Nigeria, were analyzed by flash pyrolysis-gas chromatography (Py-GC) method in order to unravel its geochemical history and properties. The distributions of the initial biomarkers of the original oils from the pyrolysates are related to the assessment of organic matter source, paleo-redox conditions and source environment during deposition. Also, it effectively establishes the genetic relationship of the bitumens. The n-alkane distributions in the pyrolysates reveal nC₉-nC₃₂ n-alkanes, maximizing at nC₁₄, isoprenoids-pristane (Pr) and phytane (Ph), and some n-alkene peaks. High peaks of low to medium-weight nC₉-nC₂₀ n-alkanes and low peaks of nC₂₁₊ n-alkanes characterize the distributions. These reveal that abundant algal organic matter with some terrigenous inputs contributed to the source rock of the bitumens. The high concentration of marine organic matter inputs to the source rock is further confirmed by the nC₁₇/nC₂₇ ratios which range from 5.39 to 19.82 and shows the predominance of nC₁₇ alkanes. The general unimodal n-alkane distributions in the bitumens indicate derivation from similar organic matter types showing that they are genetically related. The anoxic to suboxic environmental conditions that prevailed during the deposition of the sediments is revealed by the isoprenoids, Pr/Ph ratios (0.72–1.28). Pristane/nC₁₇ and Phytane/nC₁₈ range from 0.16 to 0.33 and 0.22 to 0.56, revealing that the bitumens were from predominantly marine organic matter (type II kerogen) preserved in a reducing environment with no evidence of biodegradation. However, the Ph/nC₁₈ ratio and the cross plot of Pr+Ph/nC₁₇+nC₁₈ allow the classification of the bitumens into two subfamilies/groups (A and B). The bitumen samples have low wax content as indicated by the degree of waxiness ranging from 0.21 to 0.38 which confirms low terrigenous input. Based on the carbon preference index (CPI: 0.92 to 1.55) and odd-even predominance (OEP: 0.70 to 1.36), it is concluded that the bitumens are immature to marginally mature.

Conformance control or water shut-off is a technique used to improve oil recovery. During conformance control, polymers block high permeability water areas and redistribute water drive toward unswept oil zones. In this study, co-polymers (denoted ATP-PGV/AM-co-AMPS) were synthesized using acrylamide (AM) and 2-acrylamide-2-methylpropane sulfonic acid (AMPS) as the monomers, polyethylene glycol (PEG)-200 and methylenebisacrylamide (MBA) as the crosslinkers, attapulgite (ATP) and bentonite (PGV) as the clay types, and ammonium persulfate (APS) as the initiator, in addition to paraffin oil and surfactants. Samples were synthesized using inverse emulsion polymerization with different concentrations of monomers, crosslinkers, and clays, and they were characterized using Fourier-transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX). FTIR spectra of the samples confirmed the existence of sulfonate and hydroxyl groups, which are important for polymer swelling. SEM-EDX images indicated that the morphology and elemental composition were different before and after swelling, confirming the occurrence of swelling. Moreover, samples were placed in sodium chloride solution (20,000 ppm) for 7 days to evaluate swelling at both room temperature and 90 °C. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used to determine the thermal characteristics of the microparticles. Finally, rheological measurements were used to assess the deformation and rheological behavior of the hydrogels. The results showed that after 1 day, good swelling without loss of mechanical strength was achieved with the composite synthesized using 10% AM, 15% AMPS, 6% PGV, and 10% ATP.