bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigation of Cleanup Efficiency of Hydraulically Fractured Wells in Gas Condensate Reservoirs
Authors: Ghahri P. , Jamiolahmady M. , Sohrabi M. 
Published: May 2009

Abstract
In tight gas reservoirs, gas well production after hydraulic fracturing (HF) is often greatly impaired, through various mechanisms by invasion of fracturing fluid (FF) into the matrix and fracture and poor cleanup efficiency. In the last four decades, fracture face damage and fracture conductivity impairment has been considered as the main sources of such poor performance albeit with conflicting reports on the relative significance of these two effects. Furthermore, there are still several important issues, which have been either overlooked or not properly addressed in this process.
The scope of this study is to investigate the performance of cleanup efficiency in gas and gas condensate reservoir during HF. A single-well model was constructed using ECLIPSE300 compositional numerical simulator to conduct a comprehensive sensitivity study on pertinent parameters. The effect of FF depth of invasion and its negative impact on the fracture permeability (kf), matrix permeability and that of capillary pressure (Pcm), pressure drawdown, initial water saturation (Swi), FF mobility and hysteresis on the gas production from two tight rocks were investigated.
We have been able to reproduce the simulation results reported by previous investigators. However, our results demonstrated that when a more realistic FF depth of invasion into the fracture and matrix, as proposed here, was simulated the reported severe reduction in the gas production, during some of HF operations, was observed in our simulation study. Pcm increased the negative impact of FF invasion into the formation over that of the reduction in kf. If Pcm of the invaded zone was reduced using surfactants, back flow of FF improved, which impaired the out flow of gas for sometime. The negative impact of permeability reduction of the matrix invaded zone is more pronounced for the case with Swi. The improved mobility of FF and presence of condensate improved the FF recovery. These results, which verify the real causes of an ineffective cleanup, can be used for an improved planning of HF operations.
VES: An Alternative to Biopolymers in Reservoir Drill-In Fluids
Authors: Ravitz Ray , Moore LaTosha , Lu Shawn 
Published: May 2009

Abstract
A novel reservoir drill-in fluid (RDF) has been developed that utilizes viscoelastic surfactants (VES) as the primary viscosifier and as a consequence, eliminates the need to use biopolymers for viscosity. Biopolymers have been the standard RDF viscosifier for a long time. They provide stable rheological properties required for drilling and completing the reservoir section, but they have been difficult to remove as very few chemical breakers can effectively destroy the polymer chain. The VES-based viscosifier can be easily removed by a variety of non-aqueous materials, including produced hydrocarbons making this new RDF a viable alternative for a variety of openhole completion projects, particularly low-temperature and injector applications.
This new VES-based RDF system not only suspends soluble bridging material, but supplies the rheological properties necessary to transport cuttings out from the wellbore. Fluid-loss control is achieved with a novel polysaccharide starch that is compatible with the surfactant used in the system. With the addition of this particular starch, the VES-based RDF exhibits similar characteristics to a biopolymer-based RDF which also utilizes polysaccharides and soluble bridging agents, and is stable enough to withstand conventional water-based RDF contaminants.
This paper will detail the laboratory phase involved in the development of this new system. The testing confirmed that the properties normally associated with conventional biopolymer-based RDF systems are also achieved with this innovative VES RDF system. Additional testing revealed solids contamination effects and the effect that the addition of lubricants had on this unique system. Further investigation will also show the effect of a water-based filter cake breaker system currently being used in completion operations. Results of return permeability testing will also be discussed in this paper.
The development of this new RDF system showed that VES technology currently being applied in other aspects in oil and gas completion operations can now be applied in drilling the reservoir, and that this unique system can achieve the same functionality as conventional water-based RDF without the use of biopolymers.
Successful Modelling of Post-Fracture Cleanup in a Layered Tight Gas Reservoir
Authors: Shaoul Josef R. , de Koning Johan , Chapuis Christian , Rochon Jean 
Published: May 2009

Abstract
The issue of filtrate cleanup in tight-gas wells following a hydraulic fracture treatment has long been a topic of discussion in the industry. At one extreme, there is the possibility of a "water block" in which filtrate fluid prevents gas production completely. In other cases, filtrate recovery can vary over a wide range, but without apparent effect on the post-fracture production. This paper describes history matching performed on a hydraulically fractured tight gas well. Fracture growth simulations were performed with a 3D fracture model, using data from a permanent bottomhole gauge for a mini-frac and propped fracture treatment. Net pressure matching during both pumping and shut-in, based on bottomhole gauge data, gave insight into fracture geometry and resulted in two different interpretations of the net pressure data. The two different net pressure matches gave propped length estimates that varied by a factor of two. A new tool automatically generated a reservoir simulator input deck with an explicit gridded representation of the fracture for both of these cases. The model generated includes all the information needed to simulate the initial post-fracture cleanup, including the filtrate invasion profile calculated by the fracture growth model.
This reservoir simulator input deck was used to history match the measured post-fracture production test data (gas rate, water rate, bottomhole pressure). To perform the match, permeability and capillary pressure curves were adjusted for the filtrate-invaded zone and for the reservoir. Initial values for the permeability came from welltest and core results, which had given very different kh estimates. The regained permeability of the proppant pack also had to be adjusted. A reasonable match of the bottomhole pressure and the water rate during the cleanup period was obtained. The history match was good enough to allow forecast runs to be made with the same model, taking into account realistic capillary pressure behavior for the fracture fluid filtrate in the formation. These forecast simulations gave useful insights into the impact of a delayed cleanup on the longterm production behavior of a tight gas well.
Integrated Evaluation of Water Phase Trapping Damage Potential in Tight Gas Reservoirs
Authors: You Lijun , Kang Yili 
Published: May 2009

Abstract
Water phase trapping is the most vital damage to tight sandstone reservoirs, which is different from water blocking, and it is a key barrier to improve resource assessment, successful exploration and efficient development operations. It cannot be evaluated by the traditional method evaluating water blocking. This paper takes example from Daniudi tight gas reservoir in northern Ordos Basin, China. The potential tendency to water phase trapping damage is intense by the research on the geology characters such as abnormal low water saturation, pore structure. The severity of water trapping in Daniudi gas filed was proved by the experiments of the effects of water saturation on gas relative permeability, spontaneous imbibition and phase retention of water and dill-in fluids. Based on the influence mechanisms of initial water saturation, reservoir pressure, liquid properties and pore structure on water phase trapping, dimensionless phase trapping coefficient (PTC) was put forward to predict water phase trapping damage potential. The saturation and invasion depth of filtrate varying with time around wellbore were simulated, the results show that when there is no filtrate cake on the well wall the Daniudi gas reservoirs, especially P1x2+3 gas reservoir is prone to be damaged by water trapping to be wrongly evaluated or to be undervalued. In view of the theories and research results, serial measurements to prevent and treat water phase trapping are adopted to protect gas reservoirs and P1x2+3 gas reservoirs was detected to become the major pay formation. The practices of gas formation damage control verified the results of evaluation.
Water Quality and Well Injectivity: Do Residual Oil-in-Water Emulsions Matter?
Authors: Buret S. , Nabzar L. , Jada A. 
Published: May 2009

Abstract
The present work is a part of a thorough and systematic laboratory study of oil-in-water emulsion flow in porous media that we have recently undertaken to investigate the mechanisms of oil droplet retention and its consecutive impact on permeability. One of our main objectives was to see how the in-depth propagation of produced water residual dilute emulsion could impair the permeability during Produced water Reinjection (PWRI). During this casework, we used granular packs of sharp-edged silicon carbide grains and stable and dilute dodecane-in-water emulsions. The flow experiments have been performed under well-controlled conditions and we studied the effect of most of the relevant parameters including flow rate, salinity, droplet size and permeability of the porous medium.
A careful monitoring of the salinity and the jamming ratio allowed us to consider and work separately on the two main mechanisms of droplet capture, i.e. surface capture and straining capture. In a previous paper, we reported on the effect of salinity and flow rate on emulsion flow through porous media where the pore size to droplet size ratio (jamming ratio) was very high, ensuring so, that only droplet capture on pore surface is operative. This paper reports on the impact of salinity and jamming ratio on both mechanisms with the main focus on the induced permeability impairment.
We demonstrated that surface capture could induce significant in-depth permeability losses even at high jamming ratio. The maximum permeability loss reached is very sensitive to salinity and flow rate (shear thinning effect). This maximum is always lower than a limiting value dictated by the surface coverage jamming limit of RSA theory. This limiting value increases while decreasing the jamming ratio according to a simple formula extracted from the Poiseuille's law with a mean hydrodynamic thickness of the deposited layer close to the droplet diameter (monolayer deposition). Regarding the straining capture, we determined a critical jamming ratio value of 7 for this mechanism to occur. Preliminary results using only two jamming ratio values and one flow rate are presented. Compared to surface capture, the results show that straining capture induces more severe plugging with a lower rate of propagation. The lower the jamming ratio, the more severe the plugging and the lower the propagation rate. However, more investigations are still required, notably, using various jamming ratios and flow rates to better characterize this important mechanism.
Tailoring Filtrate Rheology for Invasion Control in Heavy and Light Oil Reservoirs
Authors: Moreno R. B. Z. L. , Bonet E. J. , Waldmann A. T. A. , Martins A. L. 
Published: May 2009

Abstract
The role of filtrate rheological properties on drill in fluid invasion control is mentioned by some authors as alternatives to bridging agents. Extensional viscosities and normal stress differences are some of the rheological properties of a drill in fluid which can provide extra friction in the flow through porous media, thus preventing invasion. Most of these studies present either experimental single phase validation or only include a theoretical and numerical simulation approach.
The present paper intends to add the reservoir engineering's point of view to the design of non-invasive polymeric solids free drill in fluids. An innovative experimental study, including injection experiments and CT scanning evaluation (X-Ray/2D), was carried out to investigate the role of rheology from different polymeric solutions on the invasion of different rocks - fluid reservoir systems.
Tests included two different types of polymer (one viscous and one viscoelastic); two different levels of differential pressure (in order to induce shear and extension governed flows), two levels of resident oil viscosity and different rock surface conditions (hydrophilic and hydrophobic).
Experimental results were evaluated through sensitivity models describing fluid invasion. Relevant insights and guidelines arose from the analysis of invading polymeric fluid behavior against expected shear rates and fluid's flow rates into the porous media as the response of the formation's properties and imposed gradient pressure.
Calculated data and laboratory measured data were compared and discussed in order to identify dominant parameters on drilling fluid invasion's process. Invasion depth, contact time and saturation profiles were carefully analyzed. A comprehensive analysis, based on CT scan images, of the invasion flow patterns (plug or fingering) is detailed and results indicate that viscoelastic properties may prevent invasion in heavy oils.
Formation Damage Reduction in Retrograde Gas Wells With the Use of Systematic Production Rate Changes
Authors: Quintero Luis F. , Klishch R. 
Published: May 2009

Abstract
The use of systematic changes in flow rate in a retrograde gas well can reduce the formation damage caused during drilling or completion. When a formation containing retrograde gas is drilled with water based fluids that are incompatible with the native water, a process of permeability reduction occurs. The same process may occur when the completion fluid is incompatible and the formation is perforated overbalanced. When the well is put on production the near borehole region has a pressure below the dew point of the gas. In this scenario the flow rate turbulent effects may lead to the formation of an emulsion of the precipitated oil and the invading water which cannot be reabsorbed into the gas phase even if pressure is increased by a rate reduction. These emulsion droplets can nevertheless be dislodged mechanically by creating a fatigue effect in the capillary forces that bound them to the pore throats.
This paper describes the production behavior of a retrograde gas well in a consolidated sandstone formation in the Dnieper-Donets basin which was subjected to a series of choke changes in an attempt to reduce skin. Choke sizes ranging from 3 mm to 9 mm were systematically used over a period of 7 months. The theory behind the skin reduction and the selection criteria for the choke changes is presented. Results from the well show a dramatic increase of gas rate of more than 100% over the evaluation period, while wellhead pressure also increased by 33%. The prognosis has been validated by buildup tests.
The technology presented here may be used in wells which have suffered the formation damage described above. It requires almost no capital expenditures and if properly implemented may increase the flow rate and hence the net present value of retrograde gas fields.
New Insights into Application of Foam for Acid Diversion
Authors: Farajzadeh Rouhollah , Andrianov Alexey , Bruining Hans , Zitha Pacelli L. J. 
Published: May 2009

Abstract
Foam is widely used to divert acid or abandon the high permeable layers. In this type of application foam should considerably reduce gas mobility. The nature of the gas and the surfactant may influence foaming behavior and thus the efficiency of the foam. In this paper an experimental study of the behaviorof CO2 and N2 foams in granular porous media using X-ray Computed Tomography is reported. In the experiments gas is forced through natural porous media initially saturated with a surfactant solution, a process known as SurfactantAlternatingGas (SAG). The CO2 was either under sub- or super-critical conditions whereas N2 remained under subcritical conditions in all experiments. Alpha Olefin Sulfonate (AOS) surfactant was used as foaming agent. We found that injection of gas following a slug of surfactant can considerably reduce gas mobility and promote higher liquid recovery at the experimental conditions investigated. Foaming of CO2 builds-up a lower pressure drop over the core at both low and high pressures than N2. Both gases require a certain penetration depth to develop into foam. This length is longer for N2 (larger entrance effect) and increases with growing gas velocity. Moreover, the ultimate liquid recovery by CO2 foam is always lower than by N2 foam. The possible mechanisms explaining the observed differences in foaming behavior of the two gases are discussed in detail.
Skin Free Production Through a New Gravel Pack Completion for Gas
Authors: Trieb Andreas , Philippovich Nikolaus , Überer Wolfgang , Nederlof Eduard , Thomas Florian 
Published: May 2009

Abstract
OMV-AUT is running the Schönkirchen-Reyersdorf and the Tallesbrunn gas storage facilities with capacities of 1.77 respectively 0.3 billion m3 in the Vienna basin. These facilities at depths between 1000 and 1300 meters are former sandstone gas reservoirs operated with traditional external gravel packed (GP) vertical wells. Increasing gas demand and the urge to increase efficiency prompted an effort to adapt the whole system to a state of the art operation by making full use of available technology. This included:
Application of a novel low damage drill-in fluid system Recompleting former inside as outside casing gravel packs Drilling high performance horizontal wells Completing these horizontals with an expandable sand screen (ESS) respectively with a horizontal open hole gravel pack (HOHGP)
During the project, new field quality control procedures were established and laboratory tests run to demonstrate the potential of the mud system. The mud system used had been designed for oil wells, but never before proved for gas storage. Despite many simultaneous changes in parameters, well tests confirm the assumption of substantial gains due to meticulous QC, intense cooperation and modern technology.
Improving Water Injectivity in Barrancas Mature Field with Produced Water Reinjection: A Team Approach
Authors: Cavallaro A. N. , Sitta M. , Torre I. , Palma G. , Lanza E. 
Published: May 2009

Abstract
Produced water reinjection (PWRI) is one of the most usual ways of produced water reuse in mature fields with high water cut. The relationship between water quality and injectivity decline in wells is well known and it is particularly important in mature fields, such as Barrancas, an old field located in Mendoza-Argentina, with more than 40 years of water injection. In this reservoir significant injectivity losses were recorded when fresh water was replaced by produced water in the 90's. Formation Damage mechanism is mainly caused by external cake. Particles are principally, iron sulfide, calcium carbonate, and oil droplets.
Water treatment and injection well chemical stimulation are two important contributions to oil lifting cost at Barrancas. The average water quality is quite good between water treatment plant and wells. In spite of this, injection wells require regular acidic and non acidic stimulations to restore injectivity.
To identify the causes, a team effort combining field experience, chemical and bacteriological analysis, laboratory and on site core flooding test was performed.
Through this work, water quality performance between plant and down hole well at the level of perforated zones was analyzed. Oil and solids chemical dispersants were tested during core experiments to avoid fall of injectiviy.
The experimental study has demonstrated that the use of dispersants could help to maintain water quality stability at the level of case perforations. A pilot in a selected group of wells will be implemented. It is likely to be successful.
Down-hole water quality is a critical parameter as well as the on site evaluation tests. Based on the outcome new experiences and down-hole monitoring tool will be developed.
The final goal is to improve water quality stability at the level of formation, prevent injectivity decline and reduce working pressure.
Recent Developments in the Deposition of Colloidal Asphaltene in Capillary Flow: Experiments and Mesoscopic Simulation
Authors: Wilson Alexander D. , Boek Edo S. , Ladva Hemant K. , Crawshaw John , Padding Johan T. 
Published: May 2009

Abstract
The aggregation and deposition of asphaltenic material in reservoir rock are significant problems in the oil industry and can adversely affect the producibility of a given reservoir. To obtain a fundamental understanding of this phenomenon, we have studied the deposition and aggregation of colloidal asphaltene in capillary flow by experiment and simulation. For the simulation, we have used the stochastic rotation dynamics (SRD) method, in which the solvent hydrodynamics emerge from the collisions between the solvent particles, while the Brownian motion emerges naturally from the interactions between the colloidal asphaltene particles and the solvent.
We compare our simulation results with flow experiments in glass capillaries where we use extracted asphaltenes only in toluene, re-precipitated with n-Heptane and also asphaltenes precipitated from the whole oil. In the experiments, the asphaltene precipitation and deposition dynamics were monitored in a slot capillary using optical microscopy under flow conditions similar to those used in the simulation.
Maintaining a constant flow rate of 5μL/min, we found that the pressure drop across the capillary first increased slowly, followed by a sharp increase, corresponding to a complete local blockage of the capillary. Subsequently the pressure fell sharply as asphaltenes were re-entrained. This condition was confirmed by the visual observations that showed the slow buildup of asphaltenes deposit followed by the sudden erosion of a channel through the deposit at the time when the pressure suddenly decreased.
We calculate the change in the dimensionless permeability as a function of time for both experiment and simulation. By matching the experimental and simulation results, we obtain information about 1) the interaction potential well depth for the particular asphaltenes used in the experiments, and 2) the flow conditions associated with the asphaltene deposition process. The data obtained will also be used as input parameters for a deep-bed filtration model.