查看更多>>摘要：Slightly (PM 1) to very strongly (PM 9) biodegraded crude oil was discovered in the reservoir of the Tashikula Formation in the eastern Chaiwopu Sag. The origin of oil in the eastern Chaiwopu Sag remains unclear due to different degrees of biodegradation and multi-stage nappe structure. In this study, the geochemical data from crude oil, source rocks and hydrocarbon inclusions are used to establish the correlations between oils and source rocks under complex geological conditions. The characteristics of biomarkers, isotopes and hydrocarbon inclusions reveal two stages of hydrocarbon charging in the eastern Chaiwopu Sag. Hydrocarbons formed during the first charging stage has low maturity and a relatively light carbon isotope composition, and its relative abundance of C20-23 tricyclic terpanes follows the sequence: C23 C21> C20. Hydrocarbons formed during the second charging stage is characterized by relatively high maturity and heavy carbon isotope composition, and the corresponding abundance of C20-23 tricyclic terpanes is C23< C21< C20. The biomarkers and isotopic characteristics of crude oil, source rocks and hydrocarbon inclusions reveal the hydrocarbons formed during the first charging stage originated from the Lucaogou Formation in the northern Chaiwopu Sag and the northern Bogeda Mountains, and those formed during the second charging stage originated from the Lucaogou Formation in the central Chaiwopu Sag. The high-quality source rocks and reservoirs of the Lucaogou Formation were deposited in the northern Chaiwopu Sag, which has great potential for tight/shale oil exploration.
查看更多>>摘要：Steam-based huff-and-puff technology has gained a great deal of attention in heavy oil thermal recovery, which however suffered water invasion and steam channeling. In addition, the high-temperature and -salinity seriously restrict the implementation of conventional blocking agents. Here, an innovative composite foamed gel formula consisting of a novel toughening agent is developed to adapt such harsh conditions (175 degrees C, 20 x 104 mg/L). Specifically, orthogonal testing is carried out for formula evaluation and optimization, during which the influences of component concentration, temperature, pH and salinity on the gelling time and gel strength are determined experimentally. The formation and toughening mechanism are illustrated by infrared spectroscopy and scanning electron microscopy (SEM). Blocking performances of ordinary foam, gel and novel foamed gel are compared through sandpack floodings. It is shown that the optimal formula is composed of 4.3 wt% alkali lignin, 0.35 wt% toughening agent, 4 wt% phenolic resin and 0.5 wt% foaming agent. The gel strength reaches G level at 160 degrees C after 3.5 h. The gel is still stable at 175 degrees C under a dehydration rate of 10% after one month. Even under 20 x 104 mg/L salinity, the gel strength still reaches the G level after 22 h. Much higher resistance factor of the alkali lignin foamed gel have been achieved over ordinary foam and gel. The innovative foamed gel here could adapt the harsh conditions perfectly to mitigate the adverse impacts of water invasion and steam channeling, which in turn improves the steam-based puff-and-huff efficiency significantly.
Kadyrov, RailNurgaliev, DanisSaenger, Erik H.Balcewicz, Martin...
21页
查看更多>>摘要：Well drilling with core extraction is one of the most expensive procedures in the oil industry. The potential alternative, which may open opportunities for cost-efficient acquisition of petrophysical data, can be an approach based on digital analysis of drill cuttings. The main purpose of this research was to evaluate the possibility of using digital cuttings analysis and rock physics for reservoir properties evaluation. The carbonate samples of core and cuttings were simultaneously collected from the same intervals during the drilling of deviated wells in the Carboniferous reservoir of the oil deposit in the Republic of Tatarstan, Russia. Based on the core analysis using the optical study of thin sections and XRD, we investigated sedimentological and mineralogical features and classified all lithotypes of well intervals. The standard samples were produced from all defined facies and their reservoir properties were studied in routine tests. The largest cuttings from each well interval were separated and their structures were compared using mu CT with core subsamples of the same intervals. We assessed the changes of cuttings structure occurring in the drilling process, which include the colmatation of the pore space with drilling fluid and disintegrated rock particles and the formation of secondary fractures. Detailed analysis of cuttings from one well interval consisting of the border between the facies of high porous grainstones with packstones and dense micrite limestones demonstrated that high porous varieties were eroded in the drilling process. The analysis of chemical composition using XRF-mapping, XRD and SEM with EDS showed that most of the cuttings were constituted by disintegrated rock particles or form elements (e.g. separate fusulinids) cemented by drilling mud. However, more durable cuttings from dense micrite limestones facies were generally retained their dominant calcite composition and original rock structure, with only secondary fractures. Finally, we analyzed pore space properties and performed digital simulations of wave propagation velocities to compare the characteristics of these cuttings and core subsamples from this lithotype, scanned in the same mu CT settings. The results demonstrate close characteristics of porosity 0.08-0.6%, dominant pore sizes 1-60 mu m and velocities Vp = 6130-6240 m/s, Vs = 3180-3230 m/s. However, the comparison of obtained values with measured on standard samples shows a significant difference, which is caused by deviation from REV. The potential use of cuttings for assessing reservoir and petrophysical properties can be possible in case of provision with the factors of cuttings structure alteration, representativity of samples, as well as optimization for these purposes of the drilling process with cuttings selection.
查看更多>>摘要：One of the basic challenges during drilling horizontal wellbores is the damage induced by invasion of mud filtrate into the formation. Addition of nanoparticles to drilling fluids has been recognized as a measure of control and reduction of filtrate invasion, which is the primary mechanism of the aforementioned formation damage. Despite notable advances in composing Nano-enhanced drilling fluids, the role of nanoparticle hydrophobicity on performance of the fluids has not been well studied. This study is based on a combined experimental-numerical methodology. In the experimental section, a procedure to find the optimum composition of Nano-enhanced water-based samples, containing nanoparticles of hydrophilic/hydrophobic silica and lipophilic clay to minimize the formation damage associated with mud circulation is recommended. The main idea was to investigate the effect of hydrophobicity of nanoparticles on damage reduction and furthermore, discover how other properties such as types/concentration of nanoparticles/ micro-sized additives, temperature and pressure would affect functionality and characteristics of drilling fluids. In order to more accurately and practically investigate any probable enhancements in performance of fluid samples a particular radial filtration setup was designed and used; then, functionality of mud samples was examined on grain packed porous media at radial flooding flow condition. Results revealed that samples containing 0.2 wt. % hydrophobic nanosilica had the best functionality with returned permeability of 68.4% and 51.1% for the cases of water saturated and oil saturated porous media, respectively. In the modeling section, mass balance and momentum equations were solved simultaneously by using elapsed time data. Permeability as well as thickness of mud cake formed on the wellbore wall were evaluated and compared for different Nano enhanced mud samples. Results showed that nano-enhanced drilling fluid samples generated thinner mud cakes with lower permeability values during quite shorter period of time. Results of this work might be helpful to better understand the behavior of nano-enhanced drilling fluids in radial porous systems at different conditions of nanoparticles hydrophobicity and applicable to minimize the induced formation damage during drilling of the horizontal section of a production well.
查看更多>>摘要：The Papuan Basin is the largest petmliferous basin in Papua New Guinea (PNG), where developed several sets of potential source rocks (SRs). The Jurassic SRs are clay-rich shales, whose organic matter (OM, mainly type II2-III) is predominantly derived from terrestrial higher plants deposited in a more oxic environment with relatively high maturity (0.35% < Ro < 2.03%). The Cretaceous SRs contain mixed inputs of terrigenous and marine OM (type II2-III) formed in sub-oxidized to oxidized depositional conditions with moderate maturity (0.33% < Ro < 1.58%). Whereas the Paleocene-Miocene SRs are predominant marine calcareous shales with subsidiary terrigenous OM inputs. These SRs containing type III kerogen are mostly immature (0.21% < Ro < 0.70%). The Papuan Basin oils were classified into three distinct genetic families based on biomarkers and stable carbon isotopes. Family A oils, with heavy carbon isotopes, low Pr/Ph ratios, C-29/C-27 alpha alpha alpha 20 R sterane <1.0, are likely originated from autochthonic Paleogene-Neogene mature marine OM. Family B oils have the characteristics of high Pr/Ph, moderate carbon isotopes, the dominance of C-29 alpha alpha alpha 20 R sterane, and are predominantly derived from autochthonous Jurassic SRs. Family C oils in the Eastern Papuan Fold Belt (EPFB) can be further subdivided into three subtypes by more subtle differences in specific biomarkers. Type C-1 oils, most likely stemmed from the Lower Cretaceous SRs, are characterized by light stable carbon isotopes, Pr/Ph > 2, the mild dominance of C-29 aaa 20 R sterane and the absence of oleanane +/- lupane. Type C-2 oils can be clearly distinguished from Type C-3 by C-19/(C-19 + C-23) tricyclic terpane <0.5, while the latter ones have higher abundances of oleanane +/- lupine and diahopanes as well as C-24 tetracyclic/C-23 tricyclic terpane ratios. Type C2-3 oils are originated from calcareous SRs that deposited in Late Cretaceous or younger age.
Carvalho dos Santos, Juliana MaiaRosa, Daiane RossiSchiozer, Denis JoseDavolio, Alessandra...
14页
查看更多>>摘要：In the last ten years, 4D seismic (4DS) data acquisition is evolving to permanent reservoir monitoring (PRM) systems where sensors are installed at the ocean-bottom, collecting seismic data according to the project's monitoring demand. Simultaneously, reservoir management workflows evolved to include uncertainties, where multiple reservoir models may be considered. Model-based approaches for developing and managing a field rely on error minimizations between modelled and measured data, traditionally from well production data, and eventually adapted to 4DS data. This study presents a fast, robust and unsupervised workflow to provide a comprehensive diagnosis of multiple reservoir simulation models using similarity indicators with observed 4DS. The methodology comprises a seismic forward modelling to convert hundreds of models from the reservoir engineering domain to the seismic domain. The diagnosis includes a novel region-by-region approach to compare the predicted synthetic seismic response with the observed 4DS anomalies using ternary maps generated from Gaussian mixture models (GMM), in addition to a magnitude metric. The methodology is tested in an ultra-deep turbidite field from the Campos basin in Brazil with a PRM system that captured various 4DS anomalies of different polarity, magnitude, shapes and sizes over several production and injection years. The contributions of this work are demonstrated in four applications: (1) feedback on various iterations of geomodelling, (2) feedback on well and seismic data assimilation, (3) quick evaluation of a new seismic monitor, and (4) ranking models for further decision-making studies. The workflow advantages are proved along the model-based reservoir management outline. For application (1), we successfully flagged which 4DS anomalies were being honored in the simulation models and quantified the impact of introducing features interpreted from seismic monitors in the geomodelling. For application (2), we quantified simulation model improvements provided by data assimilation. For application (3), we rapidly evaluated the quality of the seismic monitor against the existing simulation models as soon as the new seismic acquisition and processing was complete, validating the requirement to re-visit the simulation models. Finally, the workflow was crucial to select best models, out of hundreds, for the decisionmaking process, in application (4).
查看更多>>摘要：As a challenging engineering problem, the lost circulation in fractured formations seriously hinders the efficient development of oil and gas wells. Clarifying the weak layer is the key to improve lost circulation prevention and remediation. Nevertheless, due to the complexity, randomness, and interference of engineering factors, a mature lost circulation prediction method of fractured formation has not yet been formed. This work, based on geomechanical modeling, combining with logging and seismic data, constructs the three-dimensional fracture intensity spatial distribution, the three-dimensional minimum in-situ stress spatial distribution, and the threedimensional brittleness index spatial distribution of the target oilfield, respectively. At the same time, the analytic hierarchy process is used to establish a three-dimensional lost circulation risk index of the target oil field, and a classification evaluation standard for lost circulation risk is proposed. This method is applied in the Bohai A oilfield, the three-dimensional lost circulation risk index of the entire oilfield are established. Three hundred seventy-seven lost circulation sample points of drilled wells are selected, and a classification evaluation standard for lost circulation risk is established for the Bohai A oilfield. The research results show that the classification evaluation standard for lost circulation risk has good guiding significance for subsequent drilling in this area. It can scientifically guide the design of well trajectory and well structure of subsequent wells, and improve lost circulation prevention.
查看更多>>摘要：This study presents new pressure transient solutions, illustrated with some examples of the vast practical application potential. Gaussian pressure transients (GPT) are derived here to quantify the temporal and spatial propagation of instantaneous pressure changes in porous media, as initiated from cylindrical sources (vertical wells) and planar sources (hydraulic fractures). After solving the scalar pressure field in the reservoir space, and adequately accounting for the interference of the various pressure fronts by mathematical integration and superposition, the resulting pressure gradients solve for the velocity field in the reservoir space. Unique for GPT solutions is that the well rate, unlike in the traditional well-testing equations, does not appear as an input. Applying Darcy's Law, the fluid flux from the reservoir into the well and hydraulic fractures can be directly computed from the GPT solutions. The closed-form production-forecasting model can be implemented either in matrix-coded flow-visualizations of pressure depletion and flow paths for reservoir sections or in grid-less spreadsheet solutions to instantaneously generate production profiles for wells in any type of fluid injection/ extraction project (water production, geothermal energy extraction, hydrocarbon production, and fluid disposal wells). Additionally, the Gaussian method also is suitable for physics-based decline curve analysis. The practical examples included in this study are for Eagle Ford shale oil and Marcellus dry gas wells. The hydraulic diffusivities are constrained by the field data, and range between 2.36 x10(-10) and 3.48 x10(-10) m(2) s(-1) for the Eagle Ford Formation; for the Marcellus the range is 3.64x10(-9) to 5.67x10(-8) m(2) s(-1). The breakthrough solution method of Gaussian pressure transients is placed in the context of past and present modeling approaches for shale plays developed with multi-fractured wells.
查看更多>>摘要：An innovative idea is proposed for facilitating the transportation of thermally produced high-viscosity oil by injecting temperature tolerant aqueous foam. To this aim, experimental investigations of the flow characteristics of heated highly viscous oil flowing through a 25 mm i.d. horizontal rough-wall tempered borosilicate glass pipe were conducted. Measurements were made for the superficial oil and foam velocities in the range of 0.05-0.40 m/s and 0.04-0.39 m/s, respectively. Eccentric core annular flow configurations detected by a high-speed camera were found to be particularly dominant throughout the entire tested range. A two-fluid, three-zone mechanistic model for horizontal foam-oil flows was implemented for the case of shear thinning power-law fluid in the annulus, which is in accordance with the foam rheological behavior at the tested elevated temperature. Good agreement was achieved between the predicted and measured data over a wide range of operational conditions. When a complete foam annulus encapsulating the oil core is formed, a critical value of input foam volume fraction can be determined for the maximum drag reduction ratio. An optimal oil core-to-pipe radius ratio range was determined for the highest oil-transport operational coefficient. The drag reduction performance of the tested hot oil-foam system is better than that obtained with the oil-foam system employed at room temperature.
查看更多>>摘要：In recent years, to further increase the rate of penetration (ROP), cyclic electrohydraulic shockwaves drilling (EHSD) has been proposed. It is of great significance to study the rock breaking characteristics of this technology. Firstly, a series of experiments were carried out using three different types of sandstone rock samples. The results showed that all the rock samples were fractured after 15 to 40 impacts. Before fracture, the damage of rock samples can be divided into internal damage and external damage, including surface pits, orthogonal central tensile cracks developed from the bottom face, and other tensile cracks. Secondly, based on stress wave theory, a theoretical model for calculating the P-wave peak stress in the rock sample was established, and the calculation was carried out by MATLAB. The simulation results for S2-1 showed that the maximum transmitted compressive stress near the top face reaches 163.5 MPa. The P-wave reflected from the lateral faces formed a superposition area of tensile stress, and the maximum tensile stress reaches 5.44 MPa. With the increase of impact times, the maximum tensile stress gradually decreases and approaches the top face, which explains the formation of the orthogonal central cracks. In addition, it was found that rock samples are subject to the alternating changes of compressive and tensile stress under a single impact. Finally, based on the analysis and discussion of the above results, the rock breaking mechanism of EHSD was analyzed. The results showed that the EHSD mainly damages the rock through the water wedge effect, the tensile stress near the crack boundary, and alternating stress. The research can improve our understanding of how EHSD breaks rocks, which can promote the application of this technology in field drilling.
NSTL
Elsevier