Petroleum最新文献

Primary oil recovery is the first stage of hydrocarbon production in which a reservoir uses its natural energy to force hydrocarbon to its wellbore. Secondary oil recovery comes to play when hydrocarbons can no longer be further produced by natural means. The purpose of secondary recovery is to maintain reservoir pressure so as to displace hydrocarbons toward the wellbore. Both primary and secondary recovery processes cannot displace more than 50% of the available hydrocarbons in a reservoir. The remaining hydrocarbons are further recovered through Tertiary/Enhanced Oil Recovery techniques. According to literature, microbial enhanced oil recovery has been identified as a tertiary method used to improve the efficiency of hydrocarbon production from reservoirs. Microbial enhanced oil recovery is a feasible reservoir technology, which has not been widely used in the oil and gas industry owing to the attainment of the requisite reservoir conditions such as temperature within which microbes can thrive. Literature has shown that thermotolerant microbes can withstand optimum temperatures of 50–90°C, while deep and ultra-deep hydrocarbon reservoir temperatures are often above 100°C. This study identifies some isolated thermotolerant microbes from a sandstone reservoir that can withstand temperatures as high as 110°C via conventional methods and molecular analysis. The identified thermotolerant petroleum microbes: Bacillus amyloliquefaciens (A) and Bacillus nealsonii (B) were used to enhance oil recovery from a reservoir. The results showed that the microbial species A and B at a confined pressure of 3.0 MPa and temperature of 27°C, gave 46.4% and 48.6% oil recoveries, respectively, which is comparably higher than the value (26.9%) obtained for the water flooded samples. At temperatures of 80, 90, 100, 110 and 120°C, the oil recovery results show that the recovery factor (55.2%–64.1%) of species B were higher compared to the range (46.7–57.5%) recorded for species A. At the onset of the core flooding experiments, there was an initial increment in oil recovery factor as the temperature increased from 80 to 110°C, whereas, it remained constant within 110–120°C. This trend coincides with the drop in the thermal resistance exhibited by the microbes when exposed to such conditions. The cumulative oil production from the commercial Eclipse simulation closely matched those of the experiment results, whereas, the slight difference can be attributed to the adjustment of the simulation input parameters. The experimental results show that species B can be used to enhance oil recovery at reservoir temperature conditions above 100°C.

Rock abrasiveness is an important factor affecting the tool's lifetime and efficiency in breaking a rock. Characterizing rock abrasiveness helps in the design, optimization, and mean-life prediction of tools. X-ray diffraction, cast thin section analysis, and CERCHAR abrasiveness tests were performed on 18 different sandstones to characterize rock abrasiveness and explore new methods for characterization. The relationship between the mineral composition and microstructure of sandstone and abrasiveness was investigated. The results show that different structural maturities have varying effects on abrasiveness. In addition, the higher the structural maturity, the more the abrasiveness. Furthermore, in sandstones of the same structural maturity, the abrasiveness increases with equivalent quartz content (EQC). The texture coefficient (TC) and CERCHAR abrasiveness index (CAI) of sandstones with the same structural maturity showed a good linear relationship. Moreover, the correlation coefficients considering the combined parameters are above 0.85. Therefore, obtaining the microstructure and mineral composition of sandstone can effectively characterize rock abrasiveness. It also provides a new method for predicting the abrasiveness of the rock in the well.

The safety and efficiency of drilling engineering are greatly impeded by destructive vibrations of drill string in air drilling, such as stick-slip, bit-bounce and their coupled vibrations. To avoid or suppress these vibrations improving the stability of drilling operations, revealing the occurrence mechanisms of abovementioned harmful vibrations are indispensable by investigating dynamics characteristics of drill string system. In this paper, an axial-torsional coupled dynamics model that can capture the motion behaviors of bottom hole assembly (BHA) is established adopting the lumped parameter method. Subsequently, a rate of penetration (ROP) model appropriating for air drilling is obtained firstly by linear fitting means. Meanwhile, a novel discontinuous support model is established to describe the bit-formation interactions. Then, BHA dynamics are discussed using numerical simulations under different vibration scenarios: normal operation; stick-slip; bit-bounce; bit-bounce and stick-slip combination. Subsequently, in two drilling modes: the continuous and intermittent drilling, the vibration mitigation strategies and dynamics sensibility study of BHA are carried out based on the parametric analysis. The results show that increasing torsional stiffness of drill-pipes, appropriately adjusting rotation speed of top driven system and dynamic weight on bit (WOB) are deemed as an effective strategy suppressing or eliminating stick-slip and bit-bounce vibrations of BHA. Suggest that the rotation speed of top driven system and dynamic WOB are 5 rad/s and 3.5 kN, respectively. Finally, the constructed probability maps allow to driller to choose reasonable mechanical parameters, thereby realizing smooth drilling operation in the air drilling.

To further understand the characteristics of clay and sand production (hereafter collectively referred to as sand production) and to provide optimization designs of sand control schemes are critical for gas production from clayey silt natural gas hydrate reservoirs in the South China Sea. Thus, gas-water-sand production behavoirs and coupling reservoir subsidence characteristics before, during, and after hydrate dissociation of the clayey silt hydrate reservoirs with different clay contents (5%, 10%, 15%, 20%, 25%, and 30%) have been studied through a self-developed experimental system. The results show that with the increase of clay content, the total mass of sand production first increases and then decreases, and it reaches maximum when the clayey content is 20%. The sand production is the lowest before hydrate dissociation and increases significantly during hydrate dissociation, which mainly occurs in the high-speed gas and water production stage at the beginning of hydrate dissociation. After hydrate dissociation, the sand production decreases significantly. During the whole depressurization process, the clay and free sand particles generally move to the sand outlet due to the fluid driving force and overlying stress extrusion. However, for conditions of high clay contents, those particles fail to pass through the sand control screen and gradually accumulate and block the screen by forming a mud cake, which greatly reduce the permeability of the screen and limite sand production as well as gas and water production. Our research lays a foundation for sand production prediction and sand control scheme selection during gas recovery from clayey silty hydrate reservoirs that greatly need to consider a balance between sand control and gas productivity.

During the drilling process for oil and gas production, a larger number of drilling fluids invade the formation, causing severe formation damage and wellbore collapsing, which seriously hinders the efficient production of deep oil and gas. Although several plugging agents have been developed for efficient fracture sealing in recent years, the development of high-performance plugging agents with self-adaptive ability and high-temperature resistance remain a challenge. Herein, we report the synthesis of an internal rigid and external flexible plugging agent PANS by reversed-phase emulsion polymerization with nano-silica as the rigid core and poly (acrylamide-co-N-vinylpyrrolidone) as a flexible shell. The plugging agent has a median particle size of 10.5 μm and can self-adapt to seal the microfractures and fractures in the formation, leading to an effective reduction in the filtration loss of bentonite water-based drilling fluid under both low temperature and low pressure (LTLP) and high temperature and high pressure (HTHP) conditions. In addition, compared with the neat nano-silica (500 nm), the sealing efficiency of PANS toward 100–120 mesh sand bed was increased by 71.4% after hot rolling at 180°C.

In petroleum domain, optimizing hydrocarbon production is essential because it does not only ensure the economic prospects of the petroleum companies, but also fulfills the increasing global demand of energy. However, applying numerical reservoir simulation (NRS) to optimize production can induce high computational footprint. Proxy models are suggested to alleviate this challenge because they are computationally less demanding and able to yield reasonably accurate results. In this paper, we demonstrated how a machine learning technique, namely long short-term memory (LSTM), was applied to develop proxies of a 3D reservoir model. Sampling techniques were employed to create numerous simulation cases which served as the training database to establish the proxies. Upon blind validating the trained proxies, we coupled these proxies with particle swarm optimization to conduct production optimization. Both training and blind validation results illustrated that the proxies had been excellently developed with coefficient of determination, R² of 0.99. We also compared the optimization results produced by NRS and the proxies. The comparison recorded a good level of accuracy that was within 3% error. The proxies were also computationally 3 times faster than NRS. Hence, the proxies have served their practical purposes in this study.

In order to explore the effect of piston cup structure on its sealing characteristics and mechanical properties, a numerical simulation model of the piston cup in the BW-160 mud pump was established. Effects of work load, friction coefficient and cup structure parameters on the sealing and mechanical properties of the piston were discussed under mud discharge condition. The results show that stress concentration on the root and lips of the cup is becoming more and more obvious with the working load increases. The average contact pressure increases with the friction coefficient increases, but an excessive friction coefficient accelerate the wear of the cup and the heat generation. Effect of the piston lip interference and thickness on the sealing performance of the cup is greater than that of the inner wall width. The piston with groove structure can effectively improve the sealing performance of the piston. The mechanical properties of triangular groove cup are better than that of semicircular and trapezoidal groove cup.

The conglomerate rock is usually featured by strong heterogeneity, high abrasiveness, and poor drillability due to its complex composition and texture, which brought a huge challenge for drilling efficiency. In order to guide the drill bit selection and high-efficiency drilling, the physical, mechanical, and drillability characteristics were investigated for conglomerate rock that collected from the lower Jurassic Ziliujing formation in the Western Sichuan Basin of China. The mineral composition, SEM micro-structure, P- and S-wave velocities, uniaxial and triaxial compressive testing, drillability, abrasiveness were systematically tested and analyzed. The mechanical properties and anti-drilling ability of Ziliujing formation were proposed for a typical deep well of S-07, and the distribution characteristics were analyzed. The results indicated that the Ziliujing rock is rich-in quartz and clay minerals, due to the co-existing of strong quartz gravel and weak argillaceous cement, the Ziliujing rock shows strong heterogeneity. The relationships are roughly linear among UCS, drillability, and grinding weight loss with P-wave velocity. The Young's modulus, UCS, internal friction angle, drillability, and abrasiveness meet the Weibull distribution pattern, while only the Poisson's ratio meets the Kernel Smooth distribution pattern. Logging interpretation results reval that the Ziliujing formation has the Young's modulus of 38.61 ± 17.08 GPa, the Poisson's ratio of 0.327 ± 0.006, the internal friction angle of 49.21 ± 11.00°, the drillability of 8.04 ± 1.54, and the abrasiveness grade of 4.32 ± 1.94. The mechanical properties and anti-drilling ability of logging interpretation are in good agreement with the experimental data. The Ziliujing formation is a kind of hard rock with strong heterogeneity, high strength, poor drillability, and medium abrasiveness. Based on the characteristics of Ziliujing formations, the SV516TAUL PDC bit with non-planar cutters was selected for the field application due to the good abrasion resistance, impact resistance, self-sharpening and thermal stability of the non-planar cutters. The field application shows that the average ROP of the new type drill bit in Ziliujing formation is 2.93 m/h, and the average footage is 225.9 m. Comparing with the traditional PDC bit, the ROP of the new drill bit with non-planar cutters has increased by 67.4%, and the footage has increased by 92.1%. The results of this paper can be utilized to guide the drill bit selection and high-efficiency drilling in conglomerate formation.

Recently, super gas wet and gas wet surfaces have been extensively attended in petroleum industry, as supported by the increasing number of publications in the last decade related to wettability alteration in gas condensate reservoirs. In many cases, contact angle measurement has been employed to assess the wettability alteration. Even though contact angle measurement seems to be a straightforward approach, there exist many misuses of this technique and consequently misinterpretation of the corresponding results. In this regard, a critical inspection of the most recent updated concepts and the intervening parameters in the contact angle based wettability evaluation of liquid-solid-gas systems could aid to provide some remediation to alleviate this problem. To this end, this work presents a survey on the accurate terms and rigorous protocols based on the community of surface science and chemistry. As a preliminary step, advancing, receding, static, and the most stable contact angle terminology are defined. The study is followed by the definition of the contact angle hysteresis effect. The application of surface free energy in the selection of the best gas wet agent is then analyzed. Afterward, the impact of the size-dependent behavior of drop on contact angle is discussed. Finally, a sessile drop experiment is explained to achieve the defined parameters. For future contributions to petroleum industry journals, like this journal, this work could offer an easy use of the conceptual framework for analyzing the results and comparative evaluations in chemical wettability modifier agents.