查看更多>>摘要：Hydraulic Fracturing(HF)is a frequently used well stimulation technology to improve a well's productivity by increasing the contact area with the formation matrix.Hydraulic fractures are created by following a customized design based on imperfect knowledge of the subsurface formation and idealizations.Therefore,the resulting fracture system is often different from the original design,which calls for post-fracturing evaluations.Fracture diagnostics are utilized to understand fracture behavior during or after hydraulic fracturing.Understanding the geomechanics of how fractures form during fracturing has been studied in detail;however,predicting fracture genesis and propagation behavior has been a challenging endeavor because of reservoir heterogeneity.This paper will reveal the current fracture diagnostic technologies and assess their ability to detect HF extension and quantify the properties of hydraulic fractures in terms of conductivity and stimulated reservoir volumes.This paper is not an abridged version of the technical manual regarding how each method is conducted or used but focuses on insight into what they measure and their difference from others.With the critical reviews on current HF diagnostic technologies,we intend to(1)define key terminologies that are often used in HF evaluation to set up a common linguistic lexicon for comparison,@provide a brief discussion on their mechanisms;@stipulate a framework on how to choose proper HF diagnostic tools and analysis methods for different HF applications.
查看更多>>摘要：In the design of infill well trajectory in fractured area of shale gas reservoir,it is necessary to consider the problem how to bypass the fractured influence area of the old shale gas wells,as well as the problem of mutual interference between the different fractured sections during production.In this paper,the geometric model of the obstacles in fractured area of shale gas reservoir,which considers the trajectory error and fracturing effect,is established by vector algebra method.The trajectory type is classified according to positional relations among the obstacle,the directional line of initial point and target point.The trajectory optimization model for bypassing obstacles takes the minimum total well length as objective function,the safety distance to obstacle as one of the constraints.In addition,the geometric check method for judging whether there is interference between the different fractured sections is proposed based on the geometric obstacle model.Case studies have been carried out according to the field data from Fuling,and the results indicate that the trajectory optimization model in this paper can obtain the optimum trajectory to meet the needs for bypassing obstacle,minimum trajectory length and avoiding trial calculation.Besides,if the fracturing effect is ignored,the size of the obstacle will be significantly underestimated in fractured area of shale gas reservoir,which will result in drilling accidents.In sum,the obstacle model in this paper is more consistent with the situation of field fractured area drilling practice than that of the published model.This study will provide a more safer and briefer design method for optimizing the infill well trajectory in fractured area of shale gas reservoir,which is of great significance to the shale gas drilling design and drilling safety.
查看更多>>摘要：Fluid flow through nanopore structures has exhibited different behavior than that described by Darcy's law,derived from pore networks of micrometer scale.Pressure assemblies of colloidal silica spheres of specified di-ameters from 94 to 620 nanometers were prepared as model nano-porous media.The smaller silica spheres tended to form random packing,but some substantial ordering was found in the packing of the larger silica spheres.X-ray computed tomography(XCT),with a voxel resolution of 16 nm,was used to characterize the nanopore networks.The porosity of the Nano-XCT pore network(34%)was less than the total porosity of the assemblies as determined by X-ray attenuation(52%),possibly due to the limits of voxel resolution during segmentation.Fluid flow in the nanopore networks was simulated using the single-phase Lattice Boltzmann Method,and the simulated permeability was compared with the empirical and experimental values.Based on our characterization,although a well-ordered packing of silica spheres was not achieved,it was found that the nanopore networks in the colloidal silica assemblies had pore size distributions corresponding to the particle sizes.The simulated permeability was less than the experimental measurement for water flow,but the complex packing of silica spheres and surface chemistry issues need to be considered in future research.
查看更多>>摘要：Special and advanced techniques at drilling and production operations are used to drill and produce hydrocarbons from different eccentric reservoirs such as deep-water reservoirs,shale gas,and shale oil necessitates.However,these advanced techniques are considered to be costly and affecting the environment.Therefore,nanotechnology has been implemented in the drilling fluids to improve the rheological properties,hydrogen concentration,and filtration rate.This study is,therefore,aimed at evaluating the properties of zinc oxide nanoparticles and their previous implementation in drilling fluids,examining the rheological properties of water base mud from atmospheric temperature to downhole condition(90 ℃).The experiment was designed to investigate the effect of nanoparticles concentration and temperature variation on the rheological properties of water-based mud using response surface methodology.A rotational viscometer was used to measure viscosity,yield point and gel strength.Moreover,a Consistometer was used to heat the fluid sample to different temperatures reaching up to downhole condition(90 CC).It was observed experimentally that addition of zinc oxide nanoparticles impressively improved the rheological properties of water-base mud by 50% for viscosity and gel strength,and 80% for yield point.It also allowed them to maintain their quality at all temperatures.Furthermore,addition of higher concentrations of zinc oxide nanoparticles of more than 1 wt%(6 g)at low temperatures(below 40 ℃)gave the highest and most effective results of the rheological properties.
Arianna Gea PaganoGrainne El MountassirRebecca Jane Lunn
9页
查看更多>>摘要：Hydrocarbon well decommissioning requires the long-term sealing of abandoned wells.Current plug and abandonment(P&A)operations are not always able to address all potential fluid migration pathways,resulting in the possible upwards migration of hydrocarbons from formations penetrated by the wellbore.The development of innovative materials to improve well sealing remains a major challenge.This paper presents a proof of concept for the use of colloidal silica(CS)-based grout to improve the sealing performance of P&A operations.CS is a non-toxic suspension of silica nanoparticles(<100 nm)undergoing gelation upon destabilisation.Due to its excellent penetrability and controllable gel time,CS has the potential for repairing fine-aperture cracks within the cement sheath,at the cement/casing interface,or within a cement plug,where the penetration of cementitious grouts is restricted due to their relatively large particle size.In this study,the suitability of CS grout for deployment up to 1500 m depth was successfully demonstrated.Firstly,a range of CS grout mixes were investigated to test the feasibility of grout emplacement considering a timescale of 2 h for pumping operations from the surface to depth.Secondly,to investigate the sealing performance,the CS grout was injected into fractured cement cores(0.2 and 0.5 mm fracture aperture)and exposed to pressure and temperature conditions simulating downhole scenarios up to 1500 m depth(based on gradients for North Sea,UK).Fracture permeability upon water injection was assessed pre-and post-treatment.This work found that permeability values after treatment were reduced by three orders of magnitude,thus confirming the potential of CS grout for repairing fine-aperture cracks.
查看更多>>摘要：This study investigates stuck pipe mechanisms that pertain to rock cuttings under various operations.First,a transient two-layer model considering cuttings sliding down is established.The static friction of the cutting bed is derived dynamically to determine the slip point.Next,a simple method is proposed based on the wetted perimeter to obtain the pipe's different shear stresses during tripping in and out.Finally,various operations,such as pipe connections and tripping with or without circulation,are simulated flexibly by combining the pump on or off and pipe moving in or out based on an extended reach well.The results demonstrate that three kinds of tight spots due to rock cuttings are predicted precisely.The first type is cutting slippage when the pump is off.The most heavily stacked interval is at an inclination of 40°-60°,which is close to the angle of repose.The stacking height increases significantly with initial height and time,approximately 1.06-1.75 times the initial height for 10 min and as high as 1.33-4.18 times for 60 min.Second,the cuttings pile up behind the connectors,and as the diameter increases from 0.16 to 0.28 m,the bed height increases from 1.04 to 1.68 times the original height.In addition,tripping out hastens the rate of growth.The stacking height behind a connector is approximately 1.1-1.5 times the original height under a tripping speed of 0.1-0.8 m/s.Third,several dunes are formed during the iteration of drilling and washing,and the peaks are well-matched with tight spots encountered in actual drilling.The number of dunes-i.e.,the high-risk tight spots-increases with increasing well depth and decreases with increasing washing to drilling time and the flow rate.Moreover,at the surface,cuttings may emerge in 2 or more distinct waves and with a large lag between each wave during circulation.The results serve as an essential guide to predict and control tight spots more accurately for hole cleaning of stuck pipes.
查看更多>>摘要：Waxy crude oils account for about 20% of world oil reserves.Wax gelation due to pipeline operating at low ambient temperature,especially in subsea environment,is a worst-case scenario that operators fear most since the gel can potentially block the entire pipeline,if it is not managed early.Restart pressure calculation is the first step to assess severity of gelation and subsequently used to plan for the mitigation strategies which are translated into project CAPEX(Capital Expenditure)and OPEX(Operating Expenditure).Gel characteristic(i.e.rheology behaviour and gel compressibility),operating conditions(oil temperature,ambient temperature and oil flow rate)and pipeline geometry(length and diameter)are known factors governing the restart pressure calculation for a gelled waxy pipeline.Malaysian waxy crude oils are unique and have distinctive rheology which differ from waxy crude oils from odier regions mainly due to high gel yield stress of more than 500 Pa with potential failure to recovery from gelation.Hence,accurate restart pressure prediction that account for all the governing factors as well as the interplay between them,are crucial for safe operation and cost-effective mitigation strategies.A conservative approach where the entire gel is assumed to yield simultaneously is frequently used but this simple approach fails to take into account many factors,resulting in an overestimation of the restart pressure.Several improved restart pressure calculation methods have been proposed in literature.In this study,an original methodology developed by IFPEN,has been applied to predict the restart pressure of a Malaysian waxy crude oil pipeline at various conditions.The main benefit of this methodology comes from its ability to consider the conditions under which the gel has been formed,that produces a more realistic description where gel strength varies along a pipeline.The case study highlighted that Conservative laws,assuming a homogeneous gel structure everywhere in the pipe,can overestimate the restart pressure by a factor of up to 100 times than a heterogenous gel.Thanks to the 2D axisymmetric description of the pipeline gel,we showed that the shape and the location of the gel also impact the restart pressure.
查看更多>>摘要：To detect optimum well locations for new injection wells one must generally notice to existing well locations,reservoir shape,capital cost per well construction in each area as well as recovery increase relevant to new well layout.Designing injection process presents inverse optimization issue whereas adjusting exploitation wells prior to primary recovery exhibits classic optimization problem.Most important design factor namely injection well layout has no unique explicit solution to solve via analytical or numerical techniques thus one can propose meta or hyper heuristic approaches to solve such problems.Our main novelty in this work is that here we cooperate four heuristic optimization approaches with our self made fast simulation technique to optimize well locations for two exemplar miscible gas injection processes.We employ MATLAB software to construct artificial porous media prototypes with different uncertainties to investigate optimization technique performances in low rather than high risk media.Outcomes illustrate that approaches like artificial immune system or particle swarm optimization which exhibit strong local search can effectively detect optimal well locations in high risk porous media.Results also show that solution techniques such as Monte Carlo that have strong global search capabilities at expense of weak local search can discover optimum well locations only in media with low uncertainty.
查看更多>>摘要：Accurate estimation of two-phase compressibility factor(Z factor)in gas condensate reservoirs is essential for understanding phase behaviour and reliable simulation studies.Experimental measurements of Z factor in wide operational conditions are cumbersome and costly.Hence,engineers rely on existing models such as cubic equation of states(EoSs)and empirical models for estimating such important property.In this study initially the accuracy of prevalent available Z factor models for prediction of two-phase gas condensate Z factor were examined.Then,several smart models including two multilayer perceptron neural networks known as feedforward neural network(FFNN)and cascade forward neural network(CFNN)optimized with Levenberg-Marquardt(LM)and Bayesian-Regularization(BR)algorithms and one Adaptive Neuro Fuzzy Inference System(ANFIS)optimized with Particle Swarm Optimization(PSO)were developed based on 19518 data points for the same task.The databank covers gas condensate two-phase Z factor,compositional variations,molecular weight of heptane plus(MWC_(7+))and gas specific gravity in wide range of pressure and temperature.The results indicate that the FFNN-BR predicts all experimental data with high accuracy with an average absolute relative deviation of 0.321%.Furthermore,the accuracy of the developed model over two cubic EoSs and three empirical models from literature was confirmed.Finally,based on the sensitivity analysis,it was found that the pseudoreduced pressure(P_(pr)),MWC_(7+),and molar content of C_(7+)in the mixture have the highest impact on prediction of two-phase Z factor.The proposed tools can be utilized for accurate prediction of gas condensate two-phase Z factor to ensure accurate simulation studies and better phase behaviour treatments.
查看更多>>摘要：This paper presents numerical models for validating electrical resistivity(ER)-derived carbon dioxide(CO2)saturation obtained from lab-scale CO2 flooding experiments.ER assessments have generally been implemented using Archie's empirical equation,but it is only applicable to non-saline water,homogeneous medium,and non-conductive minerals.Therefore,it is necessary to develop a reliable numerical model to scale up experimental results by calibrating uncertain properties,such as capillary pressure,relative permeability,and aquifer heterogeneity.Cylindrical sandstone samples from the homogeneous Berea sandstone and heterogeneous Tako sandstone were prepared to evaluate CO2 transport within brine-saturated media.The reliability of the numerical method was verified by the trajectories of ER-derived CO2 saturation(S_(CO2))in the homogeneous Berea sandstone,which showed similar profiles and a root mean square error(RMSE)of 0.0503.The aquifer heterogeneity of the Tako sandstone influenced CO2 transport,i.e.,its frontal velocity,by producing retardation at the less porous layers,whereas the homogeneous Berea sandstone showed consistent movement of the CO2 front.The numerical simulation of the heterogeneous Tako sandstone confirmed the effects of the less porous layers and matched the experimental profiles of S_(CO2),with an RMSE of 0.0421.The developed models enable validation of ER-derived S_(CO2)at the early stage and forecasting of the CO2 distribution in heterogeneous saline aquifers.
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