查看更多>>摘要：Tarim Basin,Western China has newly discovered fracture-caved carbonate reservoirs formed by large-scale fault tectonic activity and multiple-stage karstification.The large karst caves interconnecting with tectonic fractures in series to form vertical beads-on-string structure is one of the most common patterns.Moreover,the situations of wells drilled into caves often occur during drilling.The complex geological and engineering factors cause that traditional continuum-flow models are difficult to match the recorded pressure data.To present a novel well test model to reasonably estimate reservoir parameters,this work first presents a multi-cave multi-fracture series connection physical model by simplifying complex vertical beads-on-string structure.Four kinds of mediums are considered in physical model,including large caves,small vugs,high-angle tectonic fractures and rock matrix.Thereafter,the multi-cave-multi-region model for wells drilled into vertical beads-on-string caves is developed,among of which the flow in fracture regions obeys the Darcy's law,while the flow in large caves is assumed to obey free flow.Particularly,gravity effect is considered in fracture regions because the fluids flow along vertical structure.Then we analyze the typical flow regimes and conduct sensitivity analysis on crucial parameters.Results indicate that@the new cave storage regimes,characterized by unit-slope pressure-derivative curve,are recognized.This may help identify large karst caves in field case analysis;(b)The typical feature of vertical beads-on-string structure on type curves is that cave storage regimes and linear flow regimes alternately appear;(c)large cave and vug can be distinguished by the slope of pressure derivative on type curves;(d)gravity effect could lead to unit-slope pressure and pressure derivative curves,which is traditional recognized as the presence of a closed boundary when it may not be the case.Finally,three field cases from Shunbei Oilfield in which it is difficult to achieve good fitting quality using traditional models are interpreted to verify the practicability and feasibility of the proposed model.
查看更多>>摘要：Optimal management and development plans for gas condensate reservoirs require authentic prediction for the dew point pressure(DPP).Traditionally,DPP is experimentally measured through a constant mass expansion test(CME),however,this test is relatively prohibitive and time-consuming.Equations of state and empirical correlations are employed in determining the(DPP),but due to the lack of generalized and inaccurate predictive paradigms,it is an incentive for researchers to establish new rigorous predictive models with wider applicability ranges and higher accuracy.This study tries to develop a new intelligent predictive model and to build a simple program based on 453 gas condensate samples that cover a wide range of chemical composition,reservoir temperatures,and fluid characteristics.The artificial neural network is conducted as an intelligent tool owing to its high capability and flexibility in defining the data pattern.A detailed comparison between widely used empirical correlations,PR-EOS,SRK-EOS,and the proposed new ANN model is provided in this study.Statistical and graphical analysis depicted the outstanding performance of the new model with R2 = 95.3%,ARE = 0.0069% and AARE = 5.03%.
查看更多>>摘要：As well-known,not all abandoned mines have abundant AGM resources.Also not all abandoned mines with abundant AGM resources are suitable for surface gas development.It is a very timely and valuable work on how to scientifically and quickly optimize the target abandoned mines suitable for surface development from many abandoned mines.This research includes three parts,e.g.,the development suitability evaluation of the trap in the stope,the optimization of target abandoned mine and the field application.In the first part,the evaluation system and method of trap development suitability are established.AGM resources,storage conditions,the accumulated water and the developing economy are selected as the development suitability evaluation indexes.Each evaluation index is divided into three levels,and the method to determine the grading standard value of each evaluation index is proposed.The multi-factor comprehensive evaluation method of grey relational analysis is used in the evaluation and divided the trap into three types:suitable trap,less suitable trap and unsuitable trap according to the degree of development suitability.In the second part,the optimization method of the target abandoned mine is proposed based on the theory and development suitability of the gas trap.Firstly,screen out abandoned mines with obvious safety risks or poor economic benefit prospect of gas development.Secondly,determine the number of gas traps and suitable traps in each candidate.Thirdly,the candidate abandoned mine with the largest total gas resources in suitable traps is selected as the most favorable abandoned mine.In the third part,taking a medium-sized coal mine in the southeast of Shanxi Province as a field test mine,the gas trap determination,resource calculation and development evaluation of 17 gobs were carried out.The evaluation results show that none of them are suitable trap.The results of surface gas development in the gobs of the mine confirmed the evaluation results.
查看更多>>摘要：The Miocene fluvial-deltaic system in the Bohai Bay Basin exhibits difficulties in favourable reservoir prediction in a complex strike-slip fault zone in the Tanlu fault system.On the basis of 3D seismic data and 12 wells,we utilize two different RGB colour-blending methods from various datasets.The first method is derived from the 3D stacked,-90° phase seismic volume,and the second method is generated from the root mean square(RMS)volume attribute,which is extracted from-90° phase seismic data.Combined with the linear combination analysis of user control,we attempt to better quantify reservoir thickness and evolution of the fluvial-deltaic system in the Guantao Formation.The results show that stratal slices of the second RGB colour-blending method have a much greater ability to characterize sedimentary facies evolution and to analyse sand-thickness variations,which can effectively decrease the disadvantageous influence of multiple fault blocks on stratal slice views.In the vertical section,the linear combination analysis and the first RGB colour-blending method,however,have greater utility and resolution,which can be used to characterize the sand body by the width of seismic events or display the various sand thicknesses in different colours.The high-resolution anatomy of the fluvial-deltaic system in the Bohai Bay Basin not only explains current exploration effects but also effectively predicts thick sandstones with the most production potential in this complex region.This study may also have great significance for other complex areas or strata.
查看更多>>摘要：A new qualitative Reservoir Permeability estimation approach using variational mode decomposition named RPE-VMD is proposed which directly use seismic amplitude and frequency attributes.The method reveals amplitude anomalies that may reflect details about the heterogenous distribution of reservoir permeability.The main procedure is carried out in the time-frequency domain which generates by using a generalized S transform.Reflection coefficient information is used as seismic amplitude attribute and extracted by using variational mode decomposition combined with mutual information theory from seismic data using the logarithmic spectrum.The dominant frequency extracted in the time-frequency domain is used as seismic frequency attribute for estimating reservoir thickness information.The RPE-VMD approach uses dominant reflection coefficient information from the seismic data combined with reservoir thickness information for permeability estimation.Application of this approach to field data from a sandstone reservoir in China illustrates that it can provide permeability estimation with a high resolution and accuracy.The proposed method directly uses seismic data to measure the reservoir permeability avoiding the need of seismic velocity in the conventional estimation methods.
查看更多>>摘要：This study develops a new artificial neural network(ANN)model for predicting the total organic carbon(TOC)of an organic-rich carbonate mudstone formation using conventional well log data and X-ray fluorescence spectroscopy(XRF)analysis.The data used in the study include conventional well logs,redox-sensitive elements from XRF,and TOC values measured in lab for a total of 150 core samples obtained from five wells.Selected well logs including gamma ray(GR),bulk density(RHOB),uranium(URAN),and XRF-derived elements,including molybdenum(Mo),copper(Cu),and nickel(Ni),were used to train and develop the ANN model to predict and generate continuous high-resolution TOC log profiles for the five wells.TOC data were classified into two groups based on geological descriptions and well locations.Statistical analyses were performed to establish the range of data used for each group and to evaluate relationships among the TOC and input parameters.The developed ANN model showed a high performance in providing a continuous profile of TOC.The difference between absolute average is less than 0.50 and the correlation coefficient(R-value)is greater than 0.70.Empirical correlations were extracted from the best performing ANN model,which will allow easy and quick estimation for TOC values.The developed correlations outperform available methods for determining TOC and reduce the estimation error by 42 %.
查看更多>>摘要：The authors regret<After taking fully consideration,we would like to add more co-authors after John Humphrey and before Yaser Alzayer.Their name is Abduljamiu o.Amao and Ignatius Argadestya as shown below.
查看更多>>摘要：The classical pore structure conceptual model,such as a bundle of capillaries and lattice model is challenged for applicability in unconventional reservoirs,due to the micro/nano pore scale in unconventional reservoirs,with most of them below 100nm.Meanwhile,it is important to obtain an accurate evaluation of imbibition efficiency in unconventional reservoirs since imbibition is the main method for sweeping oil in matrix.This paper improves the acyclic pore model which is more practical for unconventional reservoirs.An imbibition efficiency calculation method is proposed,the effects of bifurcation number,pore throat radii corresponding to a mercury saturation of 50%(r_(50))and wettability is studied.The mechanism about how the pore structure affects imbibition performance is revealed.Results show that the increment of bifurcation number can decelerate the imbibition time in the branch level with smaller diameter,enlarges the imbibition accessible pore size as well.As r_(50)and hydrophilic saturation increase,wetting fluid volume imbibed and driving force for imbibition is also enhanced,which results in an improvement of imbibition efficiency.
查看更多>>摘要：During the development of oil fields in permafrost regions,once the surface casing buckling occurs under the formation thawing and subsidence,it will cause great economic losses.In this paper,sinusoidal buckling of surface casing under negative friction is studied and preliminarily discussed.Based on the Winkler foundation theory and considering the different distribution forms of negative friction and soil resistance,the elastic stability model of casing is established.Combining dimensionless and Rayleigh-Ritz method,the critical slenderness ratio of sinusoidal buckling is obtained.The influence of boundary conditions,soil resistance and negative friction distribution on casing stability is quantitatively analysed on the basis of sufficient data calculation.It is found that the product of the critical slenderness ratio and the square root of the strain at the lower boundary is a fixed value which only depends on the boundary conditions and the value of soil resistance parameter,and the negative friction of different distribution forms can be superimposed according to the principle of'inverse square'of the critical slenderness ratio.On this basis,the approximate calculation formula of the critical slenderness ratio is obtained by fitting,and the average error is less than 0.4%.The numerical example shows that the increase of soil resistance will weaken the influence of negative friction distribution on the critical slenderness ratio significantly.The ability to resist sinusoidal buckling can be improved by increasing the constraint of the lower casing section and increasing the casing thickness.
查看更多>>摘要：Previous studies showed that the fouling materials strongly affect the plugging of sand control devices during the oil production,thereby reducing oil productivity index drastically.In this study,we investigate how the compressive and tensile strengths of fouling materials affect the cleaning performance of shock waves generated by an electrohydraulic stimulation(EHS)tool.First,we synthetically plug wire-wrapped screens using different class G cement slurries widely used in oil fields.Silica,calcite,clay,and organic carbon powder as additives are mixed with the cement at different concentrations.Next,we evaluate the compressive and tensile strengths of the cured cement samples by performing uniaxial compressive strength(UCS)and Brazilian tests.Finally,the cleaning performance of the EHS tool is evaluated for plugged wire-wrapped screens.The UCS and Brazilian tests results show that the presence of additives changes the mechanical properties of cement samples.The compressive and tensile strengths of cement samples prepared with silica are found to be higher than those prepared with calcite and clay.Besides,the results of the pulsing stimulation treatment performed by the EHS tool show that the cleaning performance of the EHS tool for the wire-wrapped screens plugged with cement and carbon powder is the highest among all samples as cement samples with carbon powder represent the weakest mechanical properties(UCS and tensile strengths)among all samples.This study provides valuable insights into understanding the effect of shock waves on cleaning the plugged wire-wrapped screens.The results also enable production engineers to better plan for the treatment of damaged wells.
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