Different Types Of Reservoirs Research Articles

Characterization of reservoir fluids using an EOS based on perturbation from n-alkanes

Characterization of reservoir fluids using a cubic equation of state (EOS) is conducted under unavoidable uncertainties in pressure–temperature–composition (P–T–x) space. The implicit, non-linear relationship between phase behavior predictions and adjustment parameters also makes fluid characterization non-unique and subjective. Although P–T–x space that phase behavior spans is continuous, different characterization methods have been proposed for different types of reservoir fluids.In our previous research, a method was developed for heavy-oil characterization using the Peng–Robinson (PR) EOS with the van der Waals mixing rules without volume shift. Uncertainty issues in heavy-oil characterization were addressed based on the concept of perturbation from n-alkanes (the PnA method). Pseudo components were initially assigned critical parameters that were optimized for n-alkanes in terms of liquid densities and vapor pressures using the PR EOS. The optimized reference values allowed for well-defined directions for perturbation of pseudo components’ critical parameters to match available experimental data. The robust regression algorithm required only three perturbation parameters.In this paper, we extend the PnA method to lighter fluids, such as gas condensates, volatile oils, and near-critical fluids. The main novelty of the new PnA method is that it considers proper interrelationship (ψ=a/b2) between the attraction (a) and covolume (b) parameters of pseudo components. The regression algorithm developed in this research controls the trend of the ψ parameter with respect to molecular weight using a fourth adjustment parameter γ. The ψ and γ parameters become more important for characterizing lighter fluids. For extra heavy oils, the new PnA method naturally reduces to the previous PnA method, where γ is zero.Case studies using 77 different reservoir fluids demonstrate the universal applicability, reliability, robustness, and efficiency of the new PnA method. The fluids used consist of 34 heavy and black oils, 12 volatile oils, and 31 gas condensates. Six fluids are near critical among them. The PnA method controls phase behavior predictions monotonically with parameter adjustments and systematically in P–T–x space. This is demonstrated by quantitative prediction of condensation/vaporization behavior of gas condensates and light oils and minimum miscibility pressures for various oil displacements. The PnA method requires no change in the thermodynamic model used, i.e., it can be readily implemented in existing software based on the PR EOS with the van der Waals mixing rules.We also explain how volume-shift parameters affect compositional phase behavior predictions when used as regression parameters in fluid characterization. The PnA method uses no volume shift, and properly couples volumetric and compositional phase behaviors.

Viabilities of seismic ray impedance and elastic impedance for hydrocarbon-sand discrimination

Theoretical evaluation of the elastic impedance (EI) and the ray impedance (RI) reveals that RI has a more reliable value range and is less sensitive to noise than EI. We devised a new measurement [Formula: see text] to estimate the ray impedance from elastic impedance derived by existing techniques. The recovered [Formula: see text] was expressed in the form of a normalization of EI. It solved the range variability problem of EI and had the same interpretation capability as RI. In addition, reflection coefficients represented by [Formula: see text] showed good agreement with the Zeoppritz equation even at postcritical angle of incidence. Tests of these three attributes (RI, [Formula: see text], and EI) were performed on the log data of three different types of reservoir: a typical Class III marine gas-sand, a Class I tight gas-sand, and a Class II oil-bearing sand in thin sand-mud interbedded layers. Although the crossplots of EI against acoustic impedance (AI) showed visually similar characteristics for a gas-sand as that of RI, based on the linear/quadratic discrimination analysis, RI appeared to be more applicable than EI for characterizing gas sands, especially tight gas sands. [Formula: see text], estimated from EI, had a comparable value range to the AI, and retained the interpretation ability of the original RI. Application on real seismic data showed that existing EI inversion results could be improved straightforwardly by means of the introduced transformation.

A Productivity Evaluation Model and Its Application for an Infill Horizontal Well in Different Types of Reservoirs

Productivity evaluation for infill horizontal well should take into account the interference of other oil or water wells in the flooding pattern. On the basis of the mirror-image method and source-sink theory, a semianalytical model of productivity evaluation for infill horizontal well in different types of reservoirs was built, in which the effect of boundary, the interference of other wells, the randomicity of flooding pattern, and the pressure drop along the horizontal lateral were taken into account. Application of the novel semianalytical model has demonstrated its reliability and usefulness. It is an effective method for the productivity evaluation for infill horizontal well in different types of reservoirs.

Orderliness of Hydrocarbon Accumulation Distribution in Rift Basins of Eastern China

Abstract:The Cenozoic rift basins in eastern China show a clear temporal and spatial zonation and episodic tectonic evolution, which control their episodic hydrocarbon generation and zonal accumulation. In this paper, based on the study of depositional architecture, hydrocarbon migration system and dynamic evolution in the rift basins, combinations of hydrocarbon accumulation elements were analyzed using sequence stratigraphy. Hydrocarbon distribution in system tracts with different sequence orders was further studied. And we summarized stacking patterns and horizontal combination relationships for different types of reservoirs, such as lithological, tectonic‐lithological, tectonic and stratigraphical reservoirs which can be observed from depression center to basin margin. The result reveals that various scales of pools exhibit significant distribution and evolution orderliness in different pool‐forming units, i.e., depositional systems, plays and depressions. The regular distribution of various scales of pools is closely related to tectonic evolution and depositional filling in the rift basins. The result can be applied to the fine petroleum exploration in rift basins in eastern China. It will promote the scientific prediction and evaluation of reservoir types and their spatial distribution, lead to the active shifts of exploration targets in different zones, and thus support the stable progress of fine exploration in mature exploration areas.

Development Progress of Surfactants for Chemical Combination Flooding

Chemical combination flooding is one of the main enhanced oil recovery (EOR) techniques in China. The key factor of a successful chemical combination flooding application is the development of oil displacement surfactants with good performance. In this paper, the basic requirements of surfactant for chemical combination flooding were introduced, and the development progress of surfactants for chemical combination flooding was reviewed and their application results were shown. With the expanding application of chemical combination flooding in different types of reservoir, the challenge and development direction of oil displacement surfactants were indicated.

貯留岩のタイプに対応した浸透率解析手法の検討

Petrophysical log analyses were performed on the 3 different types of reservoirs and different permeability estimation methods were applied as 3 case studies.In the case 1, based on the clear positive correlation between core porosity and core permeability, Coates equation was successfully applied. This case is an example where permeability is mainly controlled by porosity (pore volume).In the case 2, positive correlation between core porosity and core permeability are observed but there is a strong dependency on lithofacies. In order to accurately estimate permeability, facies log is required prior to log analysis and facies-dependent log analysis was performed. This case is an example where permeability is controlled by porosity but the relationship is different from facies to facies.In the case 3, there is no obvious correlation observed between core porosity and core permeability, and any facies/rock type information can not explain the scatter in porosity vs. permeability crossplot. However, there is a systematic relationship between, water saturation, capillary pressure and permeability. By generating a regression surface among these three parameters, permeability was estimated with fair accuracy. This is an example where permeability is strongly controlled by pore geometry. In this case capillary pressure vs. water saturation curve, which is strongly related to pore size distribution and possibly pore geometry, can help to estimate permeability.

Reservoirs Distribution and Hydrocarbon Accumulation of Ordovician Carbonate in Tazhong Uplift, Tarim Basin

Many types of marine carbonate reservoirs are discorvered in Tazhong Uplift, and the later alteration is obvious. The marine sources rock including the Cambrian-lower Ordovician and the mid-upper Ordovician provided a great deal of hydrocarbon for the hudrcarbon accumulation. The hydrocarbon filled into all kinds of reservoirs many times to form the different types of reservoirs in later Caledonian to early Hercynian epoch, later Hercynian to early Indo-Chinese epoch, later Yanshanian to Himalayan epoch. All these made the characteristics of hydrocarbon accumulation complex very much.

How to escape treatment

Even during effective treatment with antiretroviral drugs, low levels of HIV persist. In part, this could be due to cell-to-cell transfer of multiple virions and the drugs' inability to inhibit replication when virus levels are high. See Letter p.95 Antiretroviral therapy suppresses, but does not eradicate, HIV infection. Low-level viraemia continues for life because of the persistence of treatment-resistant reservoirs of the virus. Various different types of reservoir are thought to exist. David Baltimore and colleagues use a combination of mathematical modelling and a cell culture model of HIV infection and drug treatment to propose that ongoing HIV replication can occur in the presence of drugs if the cells become infected through cell-to-cell transmission. They propose that cell-to-cell spread of virus could be a source of localized and intermittent ongoing replication, which may show little evolution, and which could contribute to replenishment of the virus reservoir and virus persistence.

Economical Evaluation of an Oil Field Reservoir

In this study, economical evaluation of an oil field reservoir was performed using software. The software used in this study consists of different sub-programs to determine recoverable oil, recovery factor, initial and final productions, production rates, and original oil and gas in place for different types of reservoirs. Recovery efficiency was found to be 29% for water drive and 4.78% for solution gas drive reservoirs. In decline curve analysis, initial and final production rates were obtained as 40 and 20 bbl/day, respectively. The reserve is estimated as 60,000 bbls with a reserve life of 5.78 years for the field studied.

Review of Thermal Recovery Technologies for the Clearwater and Lower Grand Rapids Formations in the Cold Lake Area in Alberta

Summary Cyclic Steam Stimulation (CSS) has been a commercial recovery process since the mid 1980s in the Cold Lake area in northeast Alberta. The current bitumen production is over 220,000 B/D using CSS from this area. To achieve desired injectivity in the bitumen saturated reservoir, steam is usually injected at a pressure above or close to the fracture pressure of the formation. A relatively high pressure drawdown is created between the wellbore and formation during the production phase, particularly in the early stage of the production cycle where formation compaction and solution gas drive are the two most important recovery mechanisms. The CSS process has limited application in reservoirs with thick bottom water or in reservoirs with fine grain sands. The Steam Assisted Gravity Drainage (SAGD) process has been field tested and commercially expanded in the Lower Grand Rapids and Clearwater Formations in the Cold Lake area. In contrast to CSS, SAGD is a continuous steam injection process that relies on gravity and requires a minimum pressure drawdown to drive the reservoir fluids to the wellbore. This provides a significant advantage for SAGD as an option for the reservoirs with bottom water, top gas or with formations with fine grain sands. Several SAGD projects are in operation in different types of reservoirs in the Cold Lake and Lloydminster areas; some with thick bottom water zones. A performance review is conducted based on the available data for various CSS and SAGD projects in the Cold Lake area. The selection criteria between CSS and SAGD technologies for Clearwater and Lower Grand Rapids are discussed. Reservoir modeling results are presented concerning the impact of well placement, reservoir heterogeneity and operating parameters on SAGD performance, based on Osum's Lower Grand Rapids and Clearwater geology in the Cold Lake area.

Coherence and entanglement in a two-qubit system

Entanglement is a fundamental concept in quantum mechanics. In this review, we study various aspects of coherence and entanglement, illustrated by several examples. We relate the concepts of loss of coherence and disentanglement, via a model of two two-level atoms in different types of reservoir, including cases of both independent and common baths. Finally, we relate decoherence and disentanglement, by focusing on the sudden death of the entanglement and the dependence of the death time with the distance of our initial condition from the decoherence-free subspace. In particular, we study the sudden death of the entanglement in a two-atom system with a common reservoir.

Memory in linear recurrent neural networks in continuous time

Reservoir Computing is a novel technique which employs recurrent neural networks while circumventing difficult training algorithms. A very recent trend in Reservoir Computing is the use of real physical dynamical systems as implementation platforms, rather than the customary digital emulations. Physical systems operate in continuous time, creating a fundamental difference with the classic discrete time definitions of Reservoir Computing. The specific goal of this paper is to study the memory properties of such systems, where we will limit ourselves to linear dynamics. We develop an analytical model which allows the calculation of the memory function for continuous time linear dynamical systems, which can be considered as networks of linear leaky integrator neurons. We then use this model to research memory properties for different types of reservoir. We start with random connection matrices with a shifted eigenvalue spectrum, which perform very poorly. Next, we transform two specific reservoir types, which are known to give good performance in discrete time, to the continuous time domain. Reservoirs based on uniform spreading of connection matrix eigenvalues on the unit disk in discrete time give much better memory properties than reservoirs with random connection matrices, where reservoirs based on orthogonal connection matrices in discrete time are very robust against noise and their memory properties can be tuned. The overall results found in this work yield important insights into how to design networks for continuous time.

Paleozoic Carbonate Hydrocarbon Accumulation Zones in Tazhong Uplift, Tarim Basin, Western China

Diverse types of marine carbonate reservoirs have been discovered in the Tazhong Uplift, Tarim Basin, and late alteration of such reservoirs is obvious. The marine source rocks of the Cambrian-lower Ordovician and the middle-upper Ordovician provided abundant oil and gas for hydrocarbon accumulation. The hydrocarbons filled various reservoirs in multiple stages to form different types of reservoirs from late Caledonian to early Hercynian, from late Hercynian to early Indosininan and from late Yanshanian to Himalayan. All these events greatly complicated hydrocarbon accumulation. An analysis of the discovered carbonate reservoirs in the Tazhong Uplift indicated that the development of a reservoir was controlled by subaerial weathering and freshwater leaching, sedimentation, early diagenesis, and alteration by deep fluids. According to the origin and lateral distribution of reservoir beds, the hydrocarbon accumulation zones in the Tazhong area were identified as: karsted reservoirs, reef/bank reservoirs, dolomite interior reservoirs, and hydrothermal reservoirs. Such carbonate hydrocarbon accumulation zones are distributed mainly in specific areas of the Tazhong uplift, respectively. Because of differences in the mechanism of reservoir formation, the reservoir space, capability, type and distribution of reservoirs are often different in different carbonate hydrocarbon accumulation zones.

Improving development profit by using reservoir based completion

Abstract Implementation of well completions enabling multiple hydrocarbon reservoirs to be produced by a single well can save production cost and enhance recovery. Aiming at the characteristics of the three types of oil and gas reservoirs in the Jabung block in Indonesia, namely, gas cap oil-rim reservoirs, multiple hydrocarbon reservoirs, and heterogeneous multiple-sand reservoirs, this article puts forward optimized completion methods by using conventional technology and down-hole equipment. The new methods are able to develop multireservoir sands at the same time or successively without additional completion jobs. In addition, the novel completion enables water injection wells to selectively control injection and improve the recovery of hydrocarbons. The above strategies have been applied to different types of reservoirs, providing an effective mean for maximizing hydrocarbon recovery, controlling operating expenditures, and improving the overall benefit of development wells.

Geomodeling technology under multifactor control

Abstract Geomodeling technology under multifactor control is one kind of data processing for certain attributes modeling, which considers both the attribute data interaction and the other related data influences. So-called multifactor control includes three meanings: the attribute space formed by restrictions from other attributes; attribute derived from other related attributes; attribute model adjustment by more reasonable models of other attributes. The key points of the modeling technology are processing of all kinds of faults, analysis and processing of complicated boundaries, structure calculation of certain small lens formations controlled by structures of typical and large layers nearby etc. Model cases from different types of reservoirs in China indicate that it's easy and efficient for geologists to build delicate and reliable geological attribute models using the technology and by integrating all kinds of data related to the attribute models from static information to performance data into the original data or restriction data for geological modeling.

Scaling Laws for the Decay of Multiqubit Entanglement

We investigate the decay of entanglement of generalized N-particle Greenberger-Horne-Zeilinger (GHZ) states interacting with independent reservoirs. Scaling laws for the decay of entanglement and for its finite-time extinction (sudden death) are derived for different types of reservoirs. The latter is found to increase with N. However, entanglement becomes arbitrarily small, and therefore useless as a resource, much before it completely disappears, around a time which is inversely proportional to the number of particles. We also show that the decay of multiparticle GHZ states can generate bound entangled states.

Theory of non-Markovian decay of a cascade atom in high-Q cavities and photonic band gap materials

The dynamics of a three-level atom in a cascade configuration with both transitions coupled to a single structured reservoir of quantized field modes is treated using Laplace transform methods applied to the coupled amplitude equations. Results are also obtained from master equations by two different approaches, that is, involving either pseudomodes or quasimodes. Two different types of reservoir are considered, namely a high-Q cavity and a photonic band gap system, in which the respective reservoir structure functions involve Lorentzians. Non-resonant transitions are included in the model. In all cases non-Markovian behaviour for the atomic system can be found, such as oscillatory decay for the high-Q cavity case and population trapping for the photonic band gap case. In the master equation approaches, the atomic system is augmented by a small number of pseudomodes or quasimodes, which in the quasimode approach themselves undergo Markovian relaxation into a flat reservoir of continuum quasimodes. Results from these methods are found to be identical to those from the Laplace transform method including two-photon excitation of the reservoir with both emitting sequences. This shows that complicated non-Markovian decays of an atomic system into structured EM field reservoirs can be described by Markovian models for the atomic system coupled to a small number of pseudomodes or quasimodes.

An Analytical Model for Production Decline-Curve Analysis in Naturally Fractured Reservoirs

Summary Decline-curve-analysis models are used frequently but still have many limitations. Approaches of decline-curve analysis used for naturally fractured reservoirs developed by waterflooding have been few. To this end, a decline-analysis model derived on the basis of fluid-flow mechanisms was proposed and used to analyze the oil-production data from naturally fractured reservoirs developed by waterflooding. Relative permeability and capillary pressure were included in this model. The model reveals a linear relationship between the oil-production rate and the reciprocal of the oil recovery or the accumulated oil production. We applied the model to the oil-production data from different types of reservoirs and found a linear relationship between the production rate and the reciprocal of the oil recovery as foreseen by the model, especially at the late period of production. The values of maximum oil recovery for the example reservoirs were evaluated with the parameters determined from the linear relationship. An analytical oil-recovery model was also proposed. The results showed that the analytical model could match the oil-production data satisfactorily. We also demonstrated that the frequently used nonlinear type curves could be transformed to linear relationships in a log-log plot. This may facilitate the production-decline analysis. Finally, the analytical model was compared with conventional models.

Multiphase natural gas migration and accumulation and its relationship to diapir structures in the DF1-1 gas field, South China Sea

The Dongfang1-1(DF1-1) gas field is the largest commercial gas field yet discovered in the Yinggehai Basin, South China Sea. The gas reservoirs in the field are normally pressured Pliocene shallow marine facies fine-grained sandstones, and the main source rocks are highly over-pressured Miocene mudstones and shales. The natural gases in the reservoirs consist mainly of hydrocarbon gas, CO 2 and N 2. Geochemical data for the natural gases show that the hydrocarbon-rich gases (except for a small amount of biogas) were derived from these source rocks distributed within over-pressured zones, but gases rich in CO 2 mainly originate from the thermal decomposition of Miocene calcareous shales and pre-Tertiary carbonates at higher temperature. Fluid inclusion data for the reservoirs were used together with the regional geology, distribution of different types of reservoirs and the evolution of diapir structures to determine the episodes of gas migration and accumulation in the DF1-1 gas field. We believe that the field was formed by four episodes of gas migration and accumulation. Fluid paleopressure simulation software, designed and developed by CNOOC China Limited, was used to simulate the paleopressure history of the strata at the top of the present-day high pressure zone (a depth of 2800 m) in the DF1-1 gas field. It predicts that the first episode occurred before about 2 Ma, the second and the third episodes between 2 and 0.5 Ma, and that the CO 2-rich gases migrated into the reservoirs after 0.5 Ma. The formation and evolution of diapir structures in the Yinggehai Basin had an important influence on the migration and accumulation of natural gases in the DF1-1 gas field. Rapid deposition, gas generation in the source rocks and thermal expansion of pore-fluids caused over-pressuring in the Miocene shales in the center of the depression. This over-pressuring together with active faulting, formed diapir structures during 5–0.5 Ma. The faults and fractures related to the diapir structures provided a pathway for gas vertical migration from the deep source rocks into the DF1-1 reservoirs, and controlled the geological distribution of different types of natural gases. On this basis, a model for gas migration and accumulation is suggested for the DF1-1 gas field.

Alkyl-tert. butyl ethers as components for enhancing octane level of gasoline

29 Oils and 12 cores (11 of Miocene age and 1 of Pretertiary age), representing some 3000 cuttings samples (of Mesozoic and Tertiary age), were investigated and correlated in order to find out whether the oils from the Croatian Subbasin of the Pannonian Basin (Sava, Drava and Slavonija-Srijem depressions) belong to the same oil generative basin.The oils were trapped in different types of reservoirs of Miocene sandstones and breccias, as well as in fractured Basement.For correlation, multiparameter approach is applied including biomarkers and isotope data.According to biomarker parameters, the oils are thought to originate from similar source(s) and could be classified in one broad group. Some biodegradition has been observed for the shallowly reservoired oils. Oils are found to differentiate regarding maturity rank. Bacterially reworked marine algal material mixed with more or less of land input and deposited in more or less suboxic environment is the probable source. Isotope data subdivide the oils into a rather spread group of the Sava trough oils and into the Drava trough oils. All the oils seem to belong most probably to Miocene source rock(s).