Day 2 Wed, April 10, 2019最新文献

{"title":"Practical Upscaling of Immiscible WAG Hysteresis Parameters from Core to Full Field Scale","authors":"O. Talabi, J. Moreno, R. K. Malhotra, Boon Keat Tham","doi":"10.2118/194634-MS","DOIUrl":"https://doi.org/10.2118/194634-MS","url":null,"abstract":"\u0000 Immiscible water-alternating-gas (iWAG) flooding is often considered as a tertiary recovery technique in waterflooded or about-to-be waterflooded reservoirs to increase oil recovery due to better mobility control and potentially favorable hysteretic changes to phase relative permeabilities. In such cases, typically, reservoir simulation models already exist and have been calibrated, often modifying saturation functions during the history matching stage. However, to utilize such models in forecasting iWAG performance, additional parameters may be required. These can be acquired by simulation of WAG coreflood experiments. While in many published cases, the parameter values obtained from matching experimental results are used without modification, this may not be advisable since the parameters are only valid at the core scale at which they were obtained. This paper discusses the challenge of systematically upscaling WAG parameters obtained at core scale to an existing full field model.\u0000 In this work, we use a multi-stage upscaling process from core scale to full field scale. The first stage uses a core scale model to match ‘representative’ core flood experiments and obtain WAG parameters. The second uses a well-to-well high-resolution 1D section of the full field model populated using gridblocks of core size to generate ‘reference’ WAG performance using the unaltered WAG parameters obtained from core. The third stage uses a similar 1D model but populated using gridblocks at full field model resolution to match the results from the reference model while adjusting the WAG parameters as little as possible. Finally, a model using the full field model resolution as well as the full field relative permeability functions which, it is assumed, have been tuned to match the history and account for dispersion is used to match the reference model results and obtain final upscaled WAG parameters.\u0000 The upscaled WAG parameters obtained at the end of this multi-stage process can be used at the field scale. This process allows clear quantification of the uncertainty associated with the upscaling process. Simulations at the third stage showed that once the full field to core scale grid size ratio exceeded a certain point (2500:1), there was a marked increase in the difference between upscaled and reference model results. It was found that if WAG parameters were changed in the full field model resolution model in order to match recovery results in the reference model, Land's parameter could change by up to 10% and relative permeability reduction factor could increase by up to 30% although it is expected that this will vary from case to case. It is therefore recommended to identify and use full field model resolutions to as close to the threshold as possible. The practice of using the core scale iWAG parameters in the full field model directly could under-estimate actual recovery, and overestimate injectivity. When considering the WAG mechanism alone, the value of th","PeriodicalId":11150,"journal":{"name":"Day 2 Wed, April 10, 2019","volume":"5 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79349687","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Correlating the Performance of Friction Reducers with Source Water Chemistry","authors":"S. Hazra, Vanessa M. Madrid, T. Luzan, M. Domelen, C. Copeland","doi":"10.2118/195199-MS","DOIUrl":"https://doi.org/10.2118/195199-MS","url":null,"abstract":"\u0000 This paper provides a detailed evaluation of the impact that field source water chemistry has on the performance of friction reducers being used for hydraulic fracturing. In this research, correlations are established between friction reducer performance and source water chemical composition, allowing operators to shorten the learning curve within their fracturing operations, use the most appropriate fluid systems, and potentially mitigate job failures.\u0000 Extensive testing has been conducted to evaluate friction reducer performance in the presence of different ionic components such as calcium, magnesium, iron and chloride. Performance testing was determined by varying individual ions, as well as using source waters from multiple field locations having total dissolved solid (TDS) levels of well over 100,000 ppm. Testing parameters included friction reduction, hydration rate via viscosity, and rheological characterization for viscosifying-type friction reducers. Principal component analysis was used as statistical tool to characterize the variation in water chemistry and to establish its relationship with friction reducer performance.","PeriodicalId":11150,"journal":{"name":"Day 2 Wed, April 10, 2019","volume":"72 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84297085","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Nitrogen Cap Drilling A Managed Pressure Drilling Alternative for Highly Fractured Carbonate Reservoir","authors":"Alexey Podust, C. Starkey, J. Wood, Gareth Cameron","doi":"10.2118/194535-MS","DOIUrl":"https://doi.org/10.2118/194535-MS","url":null,"abstract":"\u0000 Nitrogen Cap Drilling (NCD) is a technique developed by Tengizchevroil (TCO) that enables drilling a highly fractured reservoir under conditions where more conventional pressurized mud cap drilling techniques are not viable. NCD is an extension of the closed hole circulating drilling (CHCD) technique (Ref SPE Paper # 79850) previously developed and used extensively by TCO for drilling a highly fractured carbonate reservoir where severe loss circulation is encountered and incurable.\u0000 CHCD is a pressurized mud cap drilling technique that relies on the ability to fill the well with a fluid density lighter than the reservoir pressure gradient in order to maintain communication with the reservoir pressure. Once the reservoir pressure gradient drops below the density of the lightest fluid available, the well will no longer support a full column of fluid to surface and an alternate drilling method must be employed.\u0000 TCO has developed NCD as a response to this operating reality in the Tengiz field. The NCD technique involves filling the annulus with a heavier than reservoir pressure gradient fluid once severe lost returns are encountered. The annulus fluid level does not reach the surface, and the resulting air gap is pressurized with nitrogen gas. This nitrogen \"cap\" is contained under the Rotating Control Device (RCD) which allows for maintaining pressure communication with the formation. Well status is continuously monitored by tracking the wellhead pressure and measuring the annulus fluid level. The bottom hole pressure is balanced by manipulating the composition of the annular fluid column and controlling the wellhead pressure.\u0000 In 2017, TCO conducted successful field trials and demonstrated that NCD is a viable technique to enable the continuation of the low reservoir pressure drilling program in Tengiz. TCO has since adopted NCD as the standard technique in wells where CHCD is not technically viable or operationally preferable. This paper will describe NCD technique development, equipment, procedures, operational implementation, and key learnings to date.","PeriodicalId":11150,"journal":{"name":"Day 2 Wed, April 10, 2019","volume":"3 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84895256","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Extension of Oil Well Economic Life by Simultaneous Production of Oil and Electricity","authors":"Kai Wang, Xingru Wu","doi":"10.2118/195211-MS","DOIUrl":"https://doi.org/10.2118/195211-MS","url":null,"abstract":"\u0000 Oil production decline and excessive water production are prevalent in mature fields and unconventional plays, which significantly impact the profitability of the wells and result in costly water treatment and disposal. To seek for a sustainable development of those wells, reducing the operation cost and extending their economic lives, this paper presents a method of synergistic production of hydrocarbon and electricity, which could harvest the unexploited geothermal energy from the produced water and transfer heat to electricity in the wellbore. Such method is cost-effective, since it does not require any surface power plant facility, and it is replicable in numerous wells including both vertical wells and horizontal wells. By simultaneous coproduction of oil and electricity, the value of existing assets could be fully developed, operation cost could be offset, and the economic life of the well could be extended.\u0000 This recently proposed method incorporated thermoelectric power generation technology and oil production. In this method, electricity could be produced by thermoelectric generator (TEG) mounted outside of the tubing wall under temperature gradient created by produced fluid and injected fluids. The aim of this paper is to illustrate the economic practicability of oil-electricity coproduction by using thermoelectric technology in oil wells based on previously proposed design. We examined the technical data of high water-cut oil wells in North Dakota and collected required information with respect to performance thermoelectric power generations. Special emphasis was placed on the key parameters related to project economics, such as thermoelectric material, length of TEG and injection rate. Sensitive studies were carried out to characterize the impact of the key parameters on project profits. We showed that by simultaneously production of oil and electricity, $234,480 of additional value could be generated without interfering with oil production.\u0000 The proposed method capitalizes on the unexploited value of produced water and generates additional benefits. This study could provide a workflow for oil and gas operators to evaluate an oil-electricity coproduction project and could act as a guidance to perform and commercialize such project to balance parts of the operation cost and extend the life of the existing assets.","PeriodicalId":11150,"journal":{"name":"Day 2 Wed, April 10, 2019","volume":"4 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76341634","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An Integrated Study of Water Coning Control with Downhole Water Sink Completion Approaches in Multilayered - Strong Water Drive Reservoir to Improve Oil Recovery","authors":"Jupriansyah Jupriansyah","doi":"10.2118/194565-MS","DOIUrl":"https://doi.org/10.2118/194565-MS","url":null,"abstract":"\u0000 A reservoir with bottom water drive mechanism has a high tendency to generate water coning effect in their production life. As a result of water coning phenomenon, the well has a low critical safe rate which limits the productivity of the reservoir. Consequently, a new innovation for completion design in an oil well with a bottom aquifer drive is needed. The author offers a Downhole Water Sink (DWS) system to solve this problem.\u0000 DWS is a dual completion design innovation where two tubing strings are installed into the well to produce both water and oil simultaneously by different tubing. The main principle of DWS is to create a stable pressure drawdown in oil and water zone so that a stable oil-water contact is formed. DWS application in a multilayered reservoir expected to be able to resolve the water coning phenomenon thus the recovery factor increased and the well becomes economic to be produced. In this paper, the study approach involved by numerical simulation within IMPES methodology (Implicit Pressure Explicit Saturation) and Thomas’s algorithm to solve iteration. Completion modeling is creating two wells on the similar coordinate in several layered reservoirs aims to produce oil and water separately on tubing on the well.\u0000 The percentage of water cut on oil production tubing is 0% while the percentage of water cut on water production tubing is 100%. This thing shows that DWS completion system will give a greater cumulative oil production in a high production rate and the oil is oil-free water. It is observed that the successful implementation of DWS in a multilayered reservoir is taken place. The well with DWS design configuration for the WDP system shows a better performance of oil productivity compares to a conventional well completion design. This result is supported by no water production observed at oil production tubing on the surface well level. There are some parameters that affect DWS system application modeling i.e. mobility ratio, vertical and absolute horizontal permeability (kv & kh) also perforation interval.\u0000 Down-Hole Water Sink is an appropriate innovation to eliminate water coning and producing oil with high recovery factor. DWS application in a multilayered reservoir with bottom aquifer driving mechanism shows a better performance of oil productivity compares to a conventional well completion design. This result is supported by no water production observed at oil production tubing on the surface well level.","PeriodicalId":11150,"journal":{"name":"Day 2 Wed, April 10, 2019","volume":"21 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91078242","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Gas Assisted Gravity Drainage GAGD for Improving Recovery from a Field in North-East India","authors":"Nabajit Baruah, D. Mandal, Smita Swarup Jena, S. Sahu","doi":"10.2118/194585-MS","DOIUrl":"https://doi.org/10.2118/194585-MS","url":null,"abstract":"\u0000 This paper examines the prospect of Gas Assisted Gravity Drainage (GAGD) process in improving recovery from a sandstone reservoir by injecting produced gas back into the crestal part of the reservoir. Besides recovery improvement, immiscible gas injection ensures near Zero Flaring strategy. The process has been found to be ideal in reservoirs with high permeability and reasonable dip to maximize oil production wherever a sufficient gas source exists. Based on the study, gas injection is recommended at the crestal part of the reservoir under study at the rate equivalent to the produced gas to maintain pressure, arrest gas cap shrinkage and improve recovery.","PeriodicalId":11150,"journal":{"name":"Day 2 Wed, April 10, 2019","volume":"83 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77134519","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evaluation of Small-Scale Gas-to-Liquid Economic Feasibility to Mitigate North Dakota Flaring Issue","authors":"Pascoela da Silva Sequeira, R. Moghanloo","doi":"10.2118/195209-MS","DOIUrl":"https://doi.org/10.2118/195209-MS","url":null,"abstract":"\u0000 The booming of shale gas production has affected the natural gas price in the United States (U.S). Natural gas price has plummeted due to the excessive capacity. On the other hand, the import of crude oil and its production of diesel, gasoline, and others are increasing. The problem lies in finding a practical, economical and efficient way of making natural gas marketable. A potential solution is Small-scale Gas-to-Liquids plants. Small-scale GTL can fulfill some of the petroleum products demand such as Gasoline, Ultra-low-sulfur diesel, and jet-fuel. Small-scale GTL plants especially can benefit countries where the gas production is higher than gas demand, yet these countries depend on imported oil.\u0000 A Monte Carlo simulation approach is used to conduct sensitivity analysis on various parameters such as the feedstock/natural gas price, plant capacity, plant efficiency, capital expenditure (CAPEX), operational expenditure (OPEX), and products selling prices. The range for natural gas prices and gasoline prices are obtained from average historical data in the United States for the past five (10) years where the shale gas production is booming. The CAPEX is attained from previous GTL project plants before using the Power-Sizing model and literature. The annual OPEX is the percentage fraction of the CAPEX. The plant capacity was chosen based on the diseconomy factor estimated from previous GTL projects. Even with the premium quality of GTL products, the selling price for the products is equal to regular crude oil products.\u0000 Economic metrics such as Net Present Value (NPV), Internal Rate of Return (IRR), Cost-to-Profit (C/P) ratio and Payback Period were used to assess the success of GTL technology at each given business case. Results showed that NPV, IRR, C/P ratio and payback period are most affected by CAPEX, products selling price, OPEX, and capacity of the plant, in respected order. Based on these case scenarios and parameters, sensitivity analysis is conducted using Monte Carlo's simulation of 10,000 iterations the results for NPV, IRR, C/P ratio and payback period showed that the GTL project is profitable. The NPVs for the GTL plant in this study are positive for all case scenarios.\u0000 It is expected that the outcome of this research would guide shale gas producers and private investors when considering GTL investment to monetize their assets in the United States and beyond.","PeriodicalId":11150,"journal":{"name":"Day 2 Wed, April 10, 2019","volume":"os-18 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87200107","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Prevent Fouling and Corrosion During Mill-Out Operations: Case Studies","authors":"Tanhee Galindo","doi":"10.2118/195205-MS","DOIUrl":"https://doi.org/10.2118/195205-MS","url":null,"abstract":"\u0000 Case studies of mill-out operations in the Permian Basin which evaluate chemical programs and processes used. Results show how existing processes and chemicals used or lack thereof, can affect equipment and undo the preventative chemical treatments used during the hydraulic fracturing process.\u0000 The study looks at field water testing performed during various mill-out operations and considered workover rig vs coiled tubing, equipment set up, water & chemicals used, and operational challenges. Water analyses were completed on the injection water and returns at various intervals of the mill-out. Effectiveness of chemical treatment was also monitored when biocide was used.\u0000 Field case studies of horizontal wells for two operators in the Permian Basin are presented. Wells were milled-out utilizing workover rigs or coiled tubing units. Testing results show the impact of equipment setup and operations process on the water quality and efficiency of the chemicals used. Water fouling was prevalent in all cases, with coiled tubing jobs showing the highest degree of water contamination and chemical inefficiency. Changes in the water treatment program during operations showed significant improvement and sustainable results. Potential corrosion of the work string due to water fouling and water composition were also observed. The effects of changes to chemical dosages were also monitored. This was important because it identified operational improvements that can reduce equipment replacement costs, reduce chemical overuse and help protect wells from fouling due to high bacteria.\u0000 These case study provides a comprehensive review of mill-out operations, which provides guidelines for improving chemical efficiency and potential of extending life of the work string.","PeriodicalId":11150,"journal":{"name":"Day 2 Wed, April 10, 2019","volume":"30 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74297812","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Electrical Interference-Emerging Threat to Pipeline","authors":"Venkateshwar reddy Gangula, Kamlesh Bera","doi":"10.2118/194646-MS","DOIUrl":"https://doi.org/10.2118/194646-MS","url":null,"abstract":"\u0000 This paper covers the problem related to AC interferences on East West Gas Pipeline (EWPL) and the mitigation measures taken for reducing / eliminating the same.\u0000 AC interference was observed in Hyderabad region due to AC EHV Transmission lines crossing EWPL, three phase transformers and Single wire earth return (SWER) single phase transformers in the vicinity of pipeline. AC PSP voltage up to 80 Volts were observed on pipeline during night hours for which various mitigation measures were taken to bring down in acceptable range.\u0000 Similarly, there is possibility of high voltage surge at station facilities along the pipeline route due to vicinity of multiple structures, long pipeline length and having multiple conducting structures at MLV stations comprising of RTD’s, die-electric isolators, impulse Tubing for power gas and associated power gas and control equipment. Surge travel to such system can result in equipment failures. Various pro-active measures to mitigate such instances were adopted on pipeline system and are implemented successfully.\u0000 This paper illustrates the extent of the risk of corrosion, surge impact due to AC interference / surge and gives insight to various methods deployed for minimizing these risks in simple and most economical way. It also highlights the need for collaboration and operational coordination between the pipeline operators and state electricity boards to resolve such issues mutually & in most effective manner.","PeriodicalId":11150,"journal":{"name":"Day 2 Wed, April 10, 2019","volume":"37 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74521528","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Combining State-of-the-Art Hybrid Bit and Positive Displacement Motors Saves 863,670 CAD Over 20 Wells in Northern Alberta, Canada","authors":"D. Blakney, Evan Cripps, Jonathan Quintero, R. D. Bradshaw, Andres Belloso, D. Glass, Maurice Hurlburt","doi":"10.2118/195237-MS","DOIUrl":"https://doi.org/10.2118/195237-MS","url":null,"abstract":"\u0000 A Canadian oil & gas operator has been setting new benchmarks drilling the vertical and tangent section of Montney horizontal wells in the Placid field of Northern Alberta. Initially, the operator drilled vertical wells to kick off point (KOP) with polycrystalline diamond compacts (PDC) and conventional mud motors. As a result of increasing well density, however, the well plans consistently required a 15° to 30° tangent section. With PDC drilling, toolface and build up rates were problematic and the sliding rate of penetration (ROP) was slow.\u0000 A Rotary Steerable System (RSS) was introduced, but despite the improved performance, the technology came at a premium cost and the severity of drilling dysfunctions generated an increase in tool failures. With falling oil prices, a more cost effective solution was required.\u0000 Hybrid bit technology, which combines the cutting mechanism of both fixed cutter and roller-cone bits, has been extensively utilized in Canada to drill build sections, providing outstanding results. They have not, however, been commonly used to drill the vertical (drill-out) and tangent sections. The operator combined a state-of-the-art hybrid bit with a mud motor to drill the interval with an 85% success rate. The combination of the hybrid bit and conventional motor, compared to PDC and RSS, resulted in a 30% cost savings to complete the interval.\u0000 The present case study outlines how hybrid bit technology development, driven by field data in a continuous improvement cycle, identifies performance opportunities, which have a significant impact on drilling time and cost savings in drill out sections. The overall objective of this current case study is to highlight the results and lessons learned throughout the implementation process.","PeriodicalId":11150,"journal":{"name":"Day 2 Wed, April 10, 2019","volume":"7 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80217919","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}