Shane J. ProchnowNickolas Scott RatermanMegan Swenberg
15页
查看更多>>摘要：An innovative, practical, and successful subsurface machine learning workflow was introduced that utilizes any structured reservoir, geologic, engineering and production data. This workflow is colloquially called the Artificial Learning Integrated Characterization Environment (ALICE), and it has changed the way Chevron manages its tight rock and unconventional assets. The workflow guides users from framing and data gathering to geospatial assembly, quality control and ingestion, then on through machine-learning feature selection, modeling, validation, and acceptance for results reporting. The ultimate products of the workflow can be visualized in both map or log (depth) space to help identify key areas for well optimization or landing zones, respectfully. The results from ALICE have been used within Chevron to aid in exploration review assessments, type curve adjustments, landing strategies, well performance lookbacks and more. A real-data example of the workflow is presented from start to finished product for the Midland Basin Wolfcamp A, a maturely developed unconventional reservoir. The ALICE workflow and products were developed through close cross-functional collaboration between business units, data science, and research components of the corporation.
查看更多>>摘要：Long-term water flooding can be inefficient due to unbalanced displacement, resulting in sub-optimal recoveries. Therefore, the quantitative characterization and evaluation method of the flow field is significant for further development and adjustment. In this study, based on streamline simulation results, decoding rules were formulated to extract streamline data. Considering the attribute feature of each node along the streamline, flow field characterization indices were constructed. And combining the fast density peaks clustering (FDPC) algorithm and silhouette coefficient (SC), a novel flow field evaluation method based on streamline clustering was proposed. Results indicated that the invalid water circulation channels and areas with developing potential in reservoirs can be identified. Besides, the distribution of flow field can also be observed, and the characteristics of the identified region can be analyzed, which provides a basis for the subsequent flow field adjustment. Meanwhile, streamlines between injection and production wells can be subdivided to describe the distribution of water displacement capacity. Based on the evaluation results of streamline clustering, Gudao oilfield adjusted the flow field through injection-production adjustment, which effectively improved the development effect of the block and increased the recovery degree from 50.3% to 52.4%. This work provides an effective evaluation method to directly characterize the displacement changes for underground flow field, and it is of great significance for the decision-making of water flooding structure adjustment and optimization.
查看更多>>摘要：Exploration for deep and ultra-deep hydrocarbon resources plays a significant role in meeting the world's increasing energy demand. Meso-Neoproterozoic strata are considered as a possible target interval for hydrocarbon exploration in deep formations. In this regard, bitumen and potential source rocks have been identified in the Meso-Neoproterozoic strata of the Ordos Basin, western North China Craton, yet the distribution and paleogeographic evolution of these strata remain unclear. In this study, recent drilling data were combined with seismic data and fieldwork to examine the paleo environment of these Meso-Neoproterozoic strata. The results indicate that the Meso-Neoproterozoic strata are mostly distributed in the southwestern part of the basin and grow thinner from the southwest to the northeast. These sediments developed in an intracontinental rift setting with four NE-trending rift troughs having formed during the Changcheng Period. Sedimentary facies during this period were mainly fluvial-deltaic, littoral-neritic marine (quartzitic), and transitional facies. In the Jixian Period, the basin was mainly a marginal depression with a narrow sedimentation range in which carbonate tidal flats and dolomites with stromatolites and siliceous interlayers developed. During the Sinian Period, the basin was a marginal depression characterized by deposition of glacial moraine conglomerate along the southwestern margin. The Changcheng System neritic facies developed in the rift margin and northern margin of the basin controlling the distribution of total organic carbon of argillaceous source rock. The determination of the distribution, characteristics, and paleogeographic evolution of Meso-Neoproterozoic sediments is conductive to the prediction of source rock distribution, and is important for hydrocarbon exploration in the Ordos Basin.
查看更多>>摘要：To comprehensively understand the evolution of sandstone porosity during sandstone matrix acidizing is of significance to the petroleum exploration. In this study, a self-designed experimental apparatus was applied to simulate the sequential water-rock reactions of sandstone under acidic erosion. A combination of methods, including the ultrasonic velocity measurement, low-temperature nitrogen absorption tests and high pressure mercury injection (HPMI) measurements, scanning electron microscopy (SEM) imaging and computed tomography (CT) scanning were used to analyze the characteristics of porosity. The X-ray diffraction (XRD) and X-ray fluorescence (XRF) was applied to analyze the variations of minerals and elemental content in the sandstone specimens, an acidity meter and coupled plasma mass spectrometry (ICP-MS) was used to measure the chemical parameters change in the reacted solution. The results show that, the acidic erosion significantly increased the porosity abundance and decreased the minerals and elements content in the sandstone specimens, and improved the aqueous elemental Ca, Na, K and Mg concentrations in the reacted solution. These effects of acidic erosion decreased with increasing reacted distance. The porosity enhancement can be primarily attribute to the depletion of minerals in sandstone, and the reduction of acidic effect is not only due to the acid consuming, but also associated with the different sensitivity of minerals in response to H+. This study can provide some experimental references to sandstone matrix acidizing, and recommend a useful tool for further research works.
查看更多>>摘要：Polygonal fault system (PFS) is confined to fine-grained strata and have significant potential for hydrocarbon plumbing systems in sedimentary basins from deeper structures to shallow-depth gas hydrate systems. Based on a three-dimensional (3D) seismic reflection dataset from the Exmouth Plateau, Northern Carnarvon Basin, NW Shelf Australia, two different tiers of PFS (PFS-I and PFS-II) are characterized in section as well as in the plan views. The PFS-I is consisted of Early Jurassic-Early Cretaceous shallow marine limestone and marl, while the PFS-II is composed of Late Cretaceous to Paleogene bathyal facies with mudstone. calcareous mudstone, marl and silty mudstone. The polygonal faults of PFS-I show relatively low amplitude reflections, which are difficult to identify in seismic amplitude sections. PFS-I can be effectively depicted via coherency sections and time slices, with a good relationship between the low coherent black anomalies and the polygonal faults. In contrast, the polygonal faults of PFS-II are characterized by high-medium amplitude and low continuity seismic reflections, which can be easily identified in the seismic profiles and coherency time slices. The polygonal faults are represented by small throws (5-15 m) and multidirectional strikes. In addition, a series of gas chimneys, pockmarks. and shallow-depth high-amplitude anomalies of the gas hydrate system have also been identified above the deeper Triassic tectonic faults and uplifts. The polygonal faults might increase the connectivity and permeability of the seal and fine-grained layers, resulting in a certain local reduction of seal integrity and an increase in the possibility of fluid leakage. The typical seismic characteristics of PFS and the shallow depth high-amplitude anomalies of the gas hydrate system indicate a significant relationship among the deep-depth Triassic thermogenic gas, the fluid flow migration, and the development of the generation of gas hydrate system.
查看更多>>摘要：Izbash's law, which has a simpler form and exhibits narrower variations of coefficients than Forchheimer's law, has been successfully used to describe nonlinear flow in rough fractures. However, the meaning of its coefficients and its relationship with Forchheimer's law are poorly understood. Based on mathematical derivations, we identified the relationship between the cubic law, Forchheimer's law, and Izbash's law. An improved, dimensionally consistent Izbash's law which can be treated as the modified cubic law was formulated by incorporating a correction coefficient mj. The value of this coefficient depends on fluid properties, fracture geometries, and flow rate, and can be used to estimate the nonlinear flow state at given flow rates, in a similar fashion to Forchheimer number (Fq). A critical mj value (mcri) of 1.1 was determined that indicates whether the nonlinear effect can be ignored. Because mj is flow-rate-dependent, it can serve to describe the local flow behaviors, whereas the Izbash's exponent m is generally treated as a constant. At the maximum flow rate for a given pressure gradient versus flow rate curve, the value of m is approximately equal to that of m_I indicating that m represents the maximum nonlinear deviation. To validate the improved Izbash's law and the relevant findings, results from four experimental studies were utilized, and numerical simulations were performed. The result of this validation suggests the rationality of the analysis. The multiscale roughness effects on the coefficients were also investigated by selecting two different sampling intervals to construct the fracture surface. It was demonstrated that secondary roughness can enhance the development of nonlinear flow and increase the value of m, while its effects are strongly dependent on internal geometrical properties.
查看更多>>摘要：Onshore ultra-deep oil and gas resource is abundant, which has become the main area for exploration and development in the future. Fracture is an important factor affecting the development of ultra-deep reservoir, and its effectiveness, as a signifcant parameter for quantitative evaluation of the reservoir, determines the production. Taking the DB-4 ultra-deep gas reservoir in Kuqa Depression as an example, through geomechanical methods, the in situ stress distribution of the wellbore is determined by using drilling data and logging data. Based on the identifcation and quantitative characterization of fracture parameters, the stress state and shear slip trend of fractures are analyzed by three-dimensional Mohr’s circle analysis technique and Mohr Coulomb criterion, so as to quantitatively evaluate the effectiveness of ultra-deep fractures. Based on above analysis, the fracture opening under the condition of fuid injection is simulated to establish the relationship between fracture effectiveness and oil and gas production capacity. The results show that the gas reservoir where Well X4 of DB-4 gas reservoir has a burial depth of more than 8,000m, a typical onshore ultra-deep gas reservoir, and it is in an environment with extreme strong in situ stress. For the Cretaceous target reservoir, the horizontal minimum principal stress ranges between 165–180 MPa and the horizontal maximum principal stress generally exceeds 200 MPa. Natural fractures of Well X4 are largely developed, and the wellbore fracture parameters show strong heterogeneity. The Well X4 has low fracture opening pressure and high fracture effectiveness on the whole. The production capacity of gas wells in the ultra-deep reservoir shows extremely obvious positively correlation with the effectiveness of fractures under the infuence of in situ stress, while it has little infuence on petrophysical properties such as porosity and reservoir thickness. Both the fracture effectiveness evaluation method and results of DB-4 ultra-deep gas reservoir is helpful to provide geological reference for the effcient development of ultra-deep oil and gas resources in Kuqa Depression, and it is of signifcance for similar ultra-deep fractured reservoirs in the world.
查看更多>>摘要：CO2 injection can be an effective technique for increasing oil recovery from unconventional reservoirs. Laboratory studies and field tests have supported the viability of this method;; however, some chemical reactions can occur due to the interaction of the injected CO2 with brine and reservoir rock minerals, which can impact and alter several reservoir attributes. Understanding possible CO2-induced reservoir petrophysical property changes is crucial for enhanced oil recovery (EOR) and gas storage. Two Middle Bakken (MB) and two Three Forks (TF) formation samples were tested to investigate changes in rock wettability. Pore Size Distribution (PSD), and effective porosity before and after exposure to CO2. We used the contact angle technique to measure the wettability state with and without CO2 exposure. The results indicate that CO2 can alter wettability and increase the hydrophilicity in both MB and TF samples. The Nuclear Magnetic Resonance (NMR) spectroscopy technique was used to determine fluid distribution before and after CO2 injection. The results confirm that carbonic acid can dissolve portions of the dolomite, calcite, and feldspar in the rock and create new micro-and nanopores. The microporosity increased by 52% and 33% for two MB samples and 10% and 22% for two TF samples, respectively, after one cycle of CO2 injection. Based on the NMR results, the effective porosity of the MB and TF samples decreased from 5.3% to 3.8% and 7.6%-6.3%, respectively, after four CO2 cycles. The dissolved CO2 can react with rock minerals and form precipitates that block some pores. This study aimed to provide a better understanding of the fundamental mechanisms that control oil recovery using CO2 injection in unconventional reservoirs.
查看更多>>摘要：We examined the stability of SiO2 and Al2O3 NPs in both deionized (DI) water and low-salinity water (LSW). Stability was evaluated by measuring absorbance, hydrodynamic diameter, and zeta potential. NP stability was also manipulated by dispersion techniques and surfactant addition. To shape our experiments and explain results, we relied on an extended version of Derjaguin, Landau, Verwey, and Overbeek theory that accounts for hydrophobic and steric interactions. We attribute the observed stability of the examined NPs in DI to their highly negative zeta potential, which maintained absorbance and hydrodynamic diameter and produced a high energy barrier (EB). In LSW, SiO2 was stable because of its hydrophilicity, which maintained the EB, while Al2O3, which is naturally hydrophobic, strongly aggregated when a decrease in zeta potential decreased the EB. After applying various dispersion methods to Al2O3, including ultrasonication. surfactant addition, heat agitation, and pH control, we observed that the best stability occurred at pH 2 with cationic and nonionic surfactant. Although Al2O3 did not show an EB under any conditions, stability nevertheless occurred after surfactant addition, which we attribute to the steric interaction and manipulation of the primary minima. In sum, our physiochemical analysis produced stable nanofluids with potential LSW flooding applications.
Dirk J. GroenendijkStefan BoutsJohannes N.M. van Wunnik
7页
查看更多>>摘要：The performance of chemicals used in chemical enhanced oil recovery (EOR) is sensitive to the local ionic environment. Divalent ions are in particular known to reduce polymer solution viscosity and methate the adsorption of surfactants and polymers to the rock surface. Here, we study whether the addition of divalent ion-complexing agents can mitigate these interactions and thus improve the performance of EOR chemicals. The addition of sodium polyacrylate (NaPA) is found to be highly effective in reducing surfactant adsorption and increasing polymer viscosity. The reduction in surfactant adsorption is attributed to a combination of divalent ion complexation and the adsorption of polyacrylate to the rock surface. The increase in polymer viscosity is also attributed to complexation of divalent ions that would otherwise interact with the polymer. Polymer flooding experiments in a limestone core show that the addition of NaPA also significantly enhances solution injectivity and propagation, thus providing a host of benefits to chemical EOR performance.
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