Reservoir Length Research Articles

Numerical study of effects of device design on drug delivery efficiency for an active dry powder inhaler

Active dry powder inhalers (DPIs) actuated by low air volume provide distinct advantages for delivering aerosols to patients with poor respiratory capacity. This work aims to investigate the effects of piercing aperture location and inlet flow rate on device-emptying, and to identify the mechanism of particle deposition in a realistic mouth-throat (MT) region. Computational fluid dynamics (CFD) is employed to predict dispersion parameters that measure turbulence intensity, and mono-sized particles are tracked by the discrete phase model (DPM). Results show that the piercing aperture location and the inlet flow rate both have significant impacts on device emptying. Strong correlations have been established between the emitted dose and flow field parameters. The pattern and distribution of the deposited particles in the realistic MT region are highly sensitive to particle size, flow rate and reservoir length. This work provides profound insights into the performance of the active DPIs and an additional perspective on device design.

Run-up and inundation generated by non-decaying dam-break bores on a planar beach

Abstract

Application of Hagstrom-Warburton high-order truncation boundary condition on time harmonic analysis of concrete arch dam-reservoir systems

PurposeSubsequently, the response of idealized Morrow Point arch dam is studied due to stream, vertical and cross-stream ground motions for reservoir bottom/sidewalls conditions of both fully reflective and absorptive. For each combination, different orders of Hagstrom–Warburton (HW) condition are evaluated from accuracy point of view by comparing them against exact solutions. It should be emphasized that normalized length of reservoir near-field region is taken as a very low value of L/H = 0.2 during this process which makes it a very challenging test for any kind of truncation boundary condition.Design/methodology/approachIn present study, dynamic analysis of concrete arch dam-reservoir systems is formulated by FE-(FE-TE) approach [i.e. finite element-(finite element-truncation element)]. In this technique, dam and reservoir are discretized by solid and fluid finite elements. Moreover, the HW high-order condition imposed at the reservoir truncation boundary. This task is formulated by employing a truncation element at that boundary. It is emphasized that reservoir far-field is excluded from the discretized model. The formulation is initially explained in details.FindingsThe trend in gaining accuracy with increase in order of HW condition were basically the same for all three types of excitations under both full reflective and absorptive reservoir bottom/sidewalls conditions. The only exception was for cross-stream excitation response which was showing less accurate results near the first major peak for moderate orders of HW (e.g. O3-2) in comparison to what was observed for responses due to symmetric excitations (stream and vertical). This is mainly attributed to the selection of evanescent-type parameters of HW condition which is based on the first symmetric mode of reservoir. However, it is noted that error diminishes even for cross-stream excitation as order increases. High orders of HW condition, such as O5-5 considered herein, generate highly accurate responses for all three possible excitations under both types of full reflective and absorptive reservoir bottom/sidewalls conditions. It is such that responses are hardly distinguishable from corresponding exact responses. This reveals that proposed FE-(FE-TE) analysis technique based on HW condition is quite successful, and one may fully rely on that for accurate and efficient analysis of concrete arch dam-reservoir systems.Originality/valueDynamic analysis of concrete arch dam-reservoir system is formulated by new method. HW high-order condition is applied for a very low and challenging reservoir length. Different orders are evaluated against exact solution with excellent agreement. Generalized matrices of truncation element are derived for FEM programmers. The method is discussed for all types of excitation and reservoir base conditions.

Computational evaluation of optimal reservoir and sink lengths for threshold current density of electromigration damage considering void and hillock formation

Reservoirs, extensions at the cathode-end, are constructed to extend the lifetime of integrated circuit (IC) lines in terms of electromigration (EM) damage. The threshold current density jth is the maximum current density that can be supported without causing EM damage due to the matching of the EM driving force and the back flow force, which is related to the atomic density gradient. In a previous study, we reported that reservoirs can affect jth. In this present study, the jth of straight Al polycrystalline lines covered with passivation was evaluated using a numerical simulation technique focusing not only on the formation of voids but also hillocks. The optimum reservoir/sink length based on ease of formation of voids and hillocks was discussed. The reservoir suppressed void formation but promoted hillock formation. Conversely, the sink suppressed hillock formation but promoted void formation. Therefore, when void and hillock formation occurred with equal case, it was considered that either no extension, or reservoir and sink of identical length were preferable for optimal threshold current density jth. Additionally, when considering the diffusivity of atoms depending on grain boundary direction, the absence of the extension represented the optimum condition because longer reservoirs/sinks produced smaller jth. When the ease of void and hillock formation changed, the critical atomic density of void and hillock formation shifted in response, causing the optimal extension length to change. It was found that the optimum extension length changed almost linearly based on the ease of void and hillock formation.

Mathematical description of a bounded oil reservoir with a horizontal well

When horizontal wells are compared with verticals wells, their production is always higher. If their performance can be improved, they can even be more productive. Considering a horizontal well in a completely bounded oil reservoir, when the well has been producing for some time and the effect of the boundaries is evident on the flow, the pressure distribution can be approximated by considering the effects of the boundaries on the flow. Considering when a pseudosteady state flow is attained this study presents a mathematical model for approximating pressure distribution for late time for a horizontal well in an oil reservoir with sealed boundaries. We use appropriate Source and Green’s functions to develop the model. The model developed show that when the flow reaches all the boundaries a pseudosteady state flow is attained and thus pressure distribution is influenced by the oil reservoir geometry especially its width and length. Considering that the thickness of the oil reservoir will be small compared to the length of the well, the oil reservoir width and length will determine the pressure response. This will influence the flow period occurring. By considering all aspects of the flow, the model can be applied to approximate the pressure distribution for as long as the well can continue producing.

Transient analysis of concrete gravity dams by Wavenumber-TD method for general excitation

In seismic analysis of concrete gravity dam and reservoir systems using finite-element models, finding an appropriate and simple reservoir upstream truncation condition has been a challenging issue for researchers. The Sommerfeld condition is the classical approach most engineers use for this purpose and it is widely available in commercial finite-element software. In 2012, Wavenumber method was proposed as an alternative approach. The main goal of the present study is to modify this approach so it can handle vertical as well as horizontal ground motions. Moreover, the aim of the study is to evaluate the performance of the approach more thoroughly in comparison to the Sommerfeld truncation boundary, especially for vertical ground motions. With this aim, Pine Flat dam in the USA is used as a typical example. Several models are considered with different values of normalised reservoir length. The dynamic loading considered is the local Taft earthquake record of 1952. Furthermore, two types of reservoir base condition – full reflective and absorptive – are adopted. Overall, this allowed for a thorough examination and evaluation of the effectiveness of the wavenumber-TD approach for seismic analysis of concrete gravity dams.

Fluid-heat dynamics and techno-economic analysis in a deep saline aquifer

Carbon dioxide sequestration is one of the most potent ways to offset global warming. Deep saline aquifers are one of the prime targets for carbon dioxide sequestration, among several storage media. Here, a reservoir simulation study was conducted on a repository – a deep saline aquifer to store carbon dioxide. The basis of the study was to evaluate the fluid flow and heat transfer mechanisms under non-isothermal conditions. Different mass and heat transfer mechanisms were studied, and diffusion and conduction were found to have profound effects on the fate of CO2. Plume height was varied along with reservoir geometry to determine their effects on the spread of the plume. Both reservoir geometry and permeability anisotropy were found to impact the plume shape. The results show that changing the reservoir geometry changed the fate of CO2. When the reservoir was made wider, solubility trapping prevailed. In contrast, when reservoir length was narrowed, residual and capillary trapping took over. Cost analysis considering a single well of the Ketzin site, Germany, was carried out to add to the existing database, along with source–sink matching.

Evaluation of the effect of reservoir length on seismic behavior of concrete gravity dams using Monte Carlo method

Evaluation of the effect of reservoir length on seismic behavior of concrete gravity dams using Monte Carlo method

Influence of crucial reservoir properties and microbial kinetic parameters on enhanced oil recovery by microbial flooding under nonisothermal conditions: Mathematical modelling and numerical simulation

In the present study, improved mathematical and numerical models are developed in order to simulate the influence of important reservoir (effective porosity and longitudinal dispersivity), fluid and microbial kinetic (Monod half-saturation constant, substrate to biomass yield coefficient and substrate inhibition) parameters on dynamics of in-Situ microbial enhanced oil recovery (MEOR) processes using Bacillus sp. in a typical sandstone reservoir. This numerical model is a novel attempt to consider the coupled effects of heat transport and substrate-inhibition kinetics on reactive-transport of microbes, substrates and biosurfactants as against the conventional models, thus making the prediction of MEOR processes more realistic and may assist in developing suitable strategies to enhance oil recovery at field scale. In addition, the present model also investigates the changes in relative permeabilities of reservoir fluids (oil and water) and fractional flow of water under the influence of nonisothermal condition, substrate inhibition, along with variations in pore-size distribution index, oil to water viscosity ratio and crude oil API gravity within reservoir during microbial flooding for estimating residual oil recovery. The present model results match significantly well, when verified, with the existing analytical and experimental results, thus proving the model's reliability. The results suggest that under nonisothermal conditions, biosurfactant production is maximum (77.8 mg ml−1) at effective reservoir porosity 23.4%, with low substrate half-saturation constant and high substrate-to-biomass yield coefficient values of 0.018 mg ml−1 and 0.8, respectively. Though biosurfactant production is reduced by more than 80% due to substrate inhibition, which is maximum at inhibition constant value 0.1 mg ml−1, residual oil-saturation is decreased by more than 90% at the end of MEOR process, thus enhancing oil displacement, mobility and hence, improved crude oil recovery. The reactive-transport of substrates, microbes and biosurfactants at injection mean fluid velocity of 1.68 m day−1, are also found to be highly sensitive to reservoir longitudinal dispersivity (αL) and maximum biosurfactants are produced (9.74 mg ml−1) at threshold αL value, 0.37 m, which corresponds to reservoir length of 50 m. Besides, a strategy is suggested to improve the oil recovery efficiency of the present in Situ MEOR approach by characterizing the reservoir for its pore size distribution index, and formation fluids (oil and water) for their viscosity ratios and crude oil API gravities, under nonisothermal and substrate inhibition conditions.

Dominating factors on well productivity and development strategies optimization in Weiyuan shale gas play, Sichuan Basin, SW China

Abstract Weiyuan shale gas play is characterized by thin high-quality reservoir thickness, big horizontal stress difference, and big productivity differences between wells. Based on integrated evaluation of shale gas reservoir geology and well logging interpretation of more than 20 appraisal wells, a correlation was built between the single well test production rate and the high-quality reservoir length drilled in the horizontal wells, high-quality reservoir thickness and the stimulation treatment parameters in over 100 horizontal wells, the dominating factors on horizontal well productivity were found out, and optimized development strategies were proposed. The results show that the deployed reserves of high-quality reservoir are the dominating factors on horizontal well productivity. In other words, the shale gas well productivity is controlled by the thickness of the high-quality reservoir, the high-quality reservoir drilling length and the effectiveness of stimulation. Based on the above understanding, the development strategies in Weiyuan shale gas play are optimized as follows: (1) The target of horizontal wells is located in the middle and lower parts of Longyi 11 (Wei202 area) and Longyi 11 (Wei204 area). (2) Producing wells are drilled in priority in the surrounding areas of Weiyuan county with thick high-quality reservoir. (3) A medium to high intensity stimulation is adopted. After the implementation of these strategies, both the production rate and the estimated ultimate recovery (EUR) of individual shale gas wells have increased substantially.

Time-Dependent Stresses From Fluid Extraction and Diffusion With Applications to Induced Seismicity

Abstract Over recent decades, it has become clear that the extraction of fluids from underground reservoirs can be linked to seismicity and aseismic deformation around producing fields. Using a simple model with uniform fluid extraction from a reservoir, Segall (1989, “Earthquakes Triggered by Fluid Extraction,” Geology, 17(10), pp. 942–946) illustrated how poroelastic stresses resulting from fluid withdrawal may be consistent with earthquake focal mechanisms surrounding some producing fields. Since these stress fields depend on the spatial gradient of the change in pore fluid content within the reservoir, both quantitative and qualitative predictions of the stress changes surrounding a reservoir may be considerably affected by assumptions in the geometry and hydraulic properties of the producing zone. Here, we expand upon the work of Segall (1989, “Earthquakes Triggered by Fluid Extraction,” Geology, 17, pp. 942–946 and 1985, “Stress and Subsidence Resulting From Subsurface Fluid Withdrawal in the Epicentral Region of the 1983 Coalinga Earthquake,” J. Geophys. Res. Solid Earth, 90, pp. 6801–6816) to provide a quantitative analysis of the surrounding stresses resulting from fluid extraction and diffusion in a horizontal reservoir. In particular, when considering the diffusion of fluids, the spatial pattern and magnitude of imposed stresses is controlled by the ratio between the volumetric rate of fluid extraction and the reservoir diffusivity. Moreover, the effective reservoir length expands over time along with the diffusion front, predicting a time-dependent rotation of the induced principal stresses from relative tension to compression along the ends of the producing zone. This reversal in perturbed principal stress directions may manifest as a rotation in earthquake focal mechanisms or varied sensitivity to poroelastic triggering, depending upon the criticality of the pre-existing stress state and fault orientations, which may explain inferred rotations in principal stress directions associated with some induced seismicity.

Mathematical Model of Carbon Dioxide Injection into a Porous Reservoir Saturated with Methane and Its Gas Hydrate

In this paper, the process of methane replacement in gas hydrate with carbon dioxide during CO2 injection into a porous medium is studied. A model that takes into account both the heat and mass transfer in a porous medium and the diffusion kinetics of the replacement process is constructed. The influences of the diffusion coefficient, the permeability and extent of a reservoir on the time of full gas replacement in the hydrate are analyzed. It was established that at high values of the diffusion coefficient in hydrate, low values of the reservoir permeability, and with the growth of the reservoir length, the process of the CH4-CO2 replacement in CH4 hydrate will take place in the frontal regime and be limited, generally, by the filtration mass transfer. Otherwise, the replacement will limited by the diffusion of gas in the hydrate.

Large dam removal and early spontaneous riparian vegetation recruitment on alluvium in a former reservoir: Lessons learned from the pre‐removal phase of the Sélune River project (France)

AbstractThe restoration of ecological continuity along the Sélune River (Normandy, France) involves the removal of two tall hydroelectric dams (36 m removed in 2019 and 16 m in 2021), a project without precedent in Europe. During the pre‐removal phase (2014–2018), we performed scientific monitoring of the vegetation that was colonizing alluvium in the former dam reservoir (length: 19 km; surface area: 151 ha).Our study aimed to analyse if spontaneous vegetation could ecologically restore the riparian zone and help maintain fine sediment after dam removal. We used colonization indicators related to vegetation structure, taxonomic richness and diversity, and composition. These indicators were calculated at two spatial scales (local, at a single site, and broad, along the reservoir). The aim was to (a) characterize the spontaneously established species pool; (b) analyse longitudinal patterns in vegetation colonization; and (c) assess temporal changes in the species community.Our results show that diverse plant communities have developed. Slight differences in longitudinal and lateral patterns existed; they were linked with habitat heterogeneity and the reservoir's slow pace of draining. We observed fast spontaneous terrestrialization, which has resulted in cover stabilization, decreased diversity, and the development of herbaceous riverbank communities, with very few invasive species. This finding suggests stabilization potential is high and passive ecological restoration could occur, at least locally. Further analyses focusing on functional traits could help inform future management decisions regarding revegetation on reservoir alluvium.

The Use of Dam Break Model to Simulate Tsunami Run-up and Scouring Around a Vertical Cylinder

This research paper deals with the use of a dam break system to generate a surge model to study tsunami run-up, run-down and scouring around a vertical cylinder. The dam break system was provided with one or two gates to store water at a predefined depth; the water could then be quickly released by opening the gates to create a tsunami surge that runs up on land. In addition, numerical simulations of dam break surges resulting from various lengths of reservoirs were conducted to obtain more findings for further analysis regarding the characteristics of the dam break surges. A vertical cylinder model was installed on the beach at 6 meter downstream of the main gate to study the scour caused by the tsunami surge. The bed material was fine sand with a 0.19 mm diameter. The results were compared with existing experimental results. The comparison indicated that the dam break surge can be used to simulate tsunami surges by adjusting the reservoir length, the reservoir depth and the water depth downstream of the gate. The ratio of the difference between the upstream and downstream water depth on one side to the length of the reservoir on the other affect the run-up height and duration. Thus, this ratio should be considered when simulating tsunami based on dam break systems. Although different in magnitude, the shape of both the surge mareogram and the velocity time history of the tsunami surge generated using dam break system was comparable with the tsunami surge induced by a solitary wave generated using a long flume. For the relatively large cylinder located at the bore location, the separation flow was strongly directed to the wall which produced significantly unsymmetrical scour result.

Anthropogenic seismicity as aftershocks for geo-resource production? Implications for Mmax estimates (reservoir impoundment cases)

SUMMARYDeveloping a model for anthropogenic seismic hazard remains an open challenge whatever the geo-resource production. We analyse the (Mmax) largest reported magnitude on each site where (RTS) Reservoir Triggered Seismicity in documented (37 events, 1933–2008), for aftershocks of reservoir impoundment loading. We relate each reservoir impoundment to its magnitude-equivalent M*reservoir = M*(Lr). We use (Lr) the reservoir length as a proxy for a rupture length of the reservoir main shock-equivallent. This latter is derived from the empirical relationship that exists for tectonic earthquake among magnitude and rupture length. We resolve (i) Mmax for RTS are bounded by M*reservoir at a 95 per cent confidence level; (ii) in average Mmax are smaller than M*reservoir by 2.2 units (iii) 50 per cent of the Mmax occurrence is within 2 ± 1 yr from the reservoir impoundment. These triggering patterns support the signature of fluid driven seismicity during the slow reservoir impoundment emerges as a weaker efficiency (larger ΔM = M*reservoir – Mmax) to trigger Mmax events than from earthquake interactions.

Evaluation of an ammonia-water absorption long-distance cooling/heating system for enhanced geothermal resources

In order to solve the problem of low utilization efficiency of Enhanced Geothermal System (EGS) and overlong distance between geothermal wells and energy demand sites. Based on the principle of Solution Transportation Absorption system (STA), this paper presented a long-distance cooling/heating system for dual-well EGS. Firstly, a comprehensive heat transfer model for the dual-well EGS system was established and a transport model of the long-distance STA system with no pipeline heat losses was introduced. Then, the optimization of energy outputs and maximum cooling/heating supply distance was performed. Results indicated that: although with the increase of injection flow rate and well depth, cooling and heating outputs capacity by the STA-EGS increased, however, the maximum cooling/heating supply distance decreased. Optimization of 6000 m well depth showed that optimal thermal reservoir length was about 150 m which could obtain the maximum capacity. Specially, the average maximum cooling and heating distances of the proposed system were 4 and 3.5 times that of conventional systems and the average pipe diameters of the STA-EGS decreased by 78.5%, which can greatly reduce delivery pump work and initial investment.

Practical solution for stabilized pseudo-steady state productivity index of multiple vertical wells depleting closed reservoirs

Abstract The objective of this paper is introducing practical solutions for stabilized pseudo-steady state productivity index and pressure behaviors and flow regimes of multiple vertical wells depleting closed rectangular reservoirs. It introduces full understanding of reservoir performance during transient and pseudo-steady state flow using pressure and pressure derivative patterns and productivity index and productivity index derivative schemes. The practical solutions proposed in this study are relied on a new approach for accurate estimation of starting time of pseudo-steady state flow and stabilized productivity index by applying productivity index derivative that converges mathematically to zero at the beginning of this flow. It is also an attempt for pointing out the optimal reservoir configuration that can give maximum stabilized pseudo-steady state productivity index for different wellbore types and distributions in the drainage area. Several analytical models are used in this study for describing pressure drop and productivity index behavior of multiple vertical wells considering different reservoir configurations and different wellbore types and locations. These wells were assumed either fully or partially penetrate the formations. These pressure models are justified to generate two pressure derivatives, one represents the derivative of time dependent pressure drop and the second represents the derivative of time-invariant pressure drop. The two derivatives are used for determining the starting time of pseudo-steady state flow and stabilized productivity index when both converge and mathematically become identical. These models are used also to generate several plots for time-invariant or stabilized pseudo-steady state productivity index for different reservoir geometries considering different wellbore conditions. The maximum stabilized productivity index is illustrated in these plots and several analytical models for the expected flow regimes are developed using pressure and pressure derivative behaviors of different reservoirs and wellbore conditions. The outcomes of this study are summarized in: 1) Developing new analytical solutions for pressure distribution in porous media drained by multiple vertical wells. 2) Developing new practical solution for estimating stabilized pseudo-steady state productivity index. 3) Understanding pressure, pressure derivative, and productivity index behavior of finite acting reservoir depleted by multiple vertical wells during transient and pseudo-steady state production. 4) Investigating the impacts of different reservoir configurations and wellbore sizes and locations as well as partial penetration on stabilized pseudo-steady state productivity index. The novel points in this study are: 1) The optimum reservoir configuration that gives the maximum stabilized productivity index is the rectangular shape reservoir with reservoir length to width ratio of ( 2 − 4 ) . 2) Starting time of pseudo-steady state and stabilized productivity index are impacted by wellbore numbers, sizes, and locations. 3) Starting time of pseudo-steady state flow is not affected by partial penetration ratio, however, stabilized productivity index is affected by this ratio. 4) Five spots pattern gives the maximum productivity index compared with other wellbore distribution patterns. 5) Productivity index of diagonally distributed wellbores is greater than the index of wellbores distributed along reservoir length.

Patterns of Reservoir‐Triggered Seismicity in a Low‐Seismicity Region of France

We analyzed the impact of the 26 largest impounded reservoirs on reservoir‐triggered seismicity (RTS) patterns in the low‐seismicity region of continental France. We treat reservoir‐triggered earthquakes as tectonic earthquakes and apply similar concepts in our analysis. Generally, the spatial extent of an aftershock zone is controlled by the mainshock rupture length. In a similar manner, we use reservoir length as an equivalent length to the rupture length to assess the spatial extent of reservoir‐triggering earthquakes and one to three reservoir lengths as a proxy for the near‐field distance where the stress change induced by reservoir impoundment may trigger seismicity. Accordingly, we define the 1Lr distance as the near‐field reservoir effect on seismicity and the 10Lr distance as the far field, null effect of reservoir stress change on background seismicity. We find that (1) about a quarter of the reservoirs trigger Mmax=2.5–4.7 within the 1Lr distance in a 15 yr space time window, and (2) as tested against a randomized series, superposed epoch analysis demonstrates a robust increase in the average seismicity rate within 2 yrs for the 1–3Lr distance from reservoirs. The reservoirs that trigger in the (⁠ 1Lr ⁠) near‐field distance are significantly larger than the nontriggering ones. While considering the distance of triggering of earthquakes from the reservoir, it is more appropriate to consider the normalized distance (the distance normalized by the reservoir length) to identify earthquake triggering reservoirs at a 1Lr distance. While considering reservoir dimensions, the reservoir length appears to be a more important parameter than the reservoir depth, as the length is proportional to the area of significant stress change. Our results suggest that the RTS mimics the aftershock sequence of a slow reservoir‐impoundment loading, with a corresponding M∗reservoir=M(Lr) mainshock magnitude. Further, when considering mainshock–aftershock interactions, our analysis and observations support that the Mmax for RTS for a given reservoir remains, on average, smaller than the reservoir magnitude equivalent.

Hole Cleaning, Torque Management Lead to Longest Extended-Reach Well in Brazil

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper OTC 28091, “The Longest Horizontal Section Ever Drilled in an Extended-Reach Well in Brazil,” by Rafael Kenupp, Affonso Lourenço, Stian Soltvedt, and Ian Thomson, Baker Hughes, a GE company, and Grazielli Simoes, Daniela L. Morosov, and Raquel Andrade, Statoil, prepared for the 2017 Offshore Technology Conference Brasil, Rio de Janeiro, 24–26 October. The paper has not been peer reviewed. Copyright 2017 Offshore Technology Conference. Reproduced by permission. The Peregrino project, located in the post-salt zone of the Campos Basin, presents immense challenges for drilling extended-reach wells. This paper shares challenges imposed by the well profile and downhole environment on the design and execution phases. Information is included about the solutions used that led to reaching the target depth as planned, including the well-planning methodology, bottomhole-assembly (BHA) design, drill-bit selection, data monitoring, and procedures for maximizing the transfer of power downhole and minimizing rock-cutting energy. Introduction The Peregrino oil field is in the BM-C-7 area of the Campos Basin. Of 47 wells drilled from two fixed platforms in the field (Peregrino A and B), 20 were from Peregrino A, where the longest horizontal sections have been drilled. The average horizontal length was 1419 m, and the operator is pushing the technical limits to extend the overall lateral stepout, increase reservoir lengths, and maximize hydrocarbon exposure. Drilling horizontal sections beyond the field average length has several additional challenges including mud quality along the sections, high friction factors, and surface-equipment operational limits. For extended-reach wells, hole-cleaning efficiency and proper torque management have been shown to be key factors for flawless execution. Proposed Approach Considering the typical well setup in off-shore Brazil, Well A-27 had a considerable total length. The planned length of the well was 8400-m measured depth (MD), with a possible extension to 8740-m MD. The landing of a 9⅝-in.-casing shoe was planned to be at 6520-m MD with approximately 82° of inclination, and the 8½-in.-section lateral displacement was to start at 5673 m from the wellhead (Fig. 1). With a possible horizontal section of 2220 m, a rotary-steerable system was to be used, with the addition of a drilling dynamics sub and a modular motor, to reduce the demanded weight on bit (WOB) and surface rate of revolution while maintaining sufficient energy at the bit. Management of torque and equivalent circulating density (ECD) would be helped by the use of 4-in. drill-pipe, which would also provide lower torque values with less cross-sectional area. The final measure required to reduce overall friction along the horizontal well path was to add lubricant to the drilling fluid to reduce metal-to-metal friction at the drillpipe/casing interaction. Lubricant was also to be added while drilling, with the idea that drops of lubricant deposited into the mudcake would help reduce friction when drill-pipe tool joints pass through.

Deep insights to transient pressure behavior and stabilized productivity index of multilateral wells in laterally and spatially anisotropic reservoirs

The objective of this paper is focusing deep insights on stabilized productivity index (PI) and transient pressure behaviors and flow regimes of multilateral wells. It introduces an integrated approach for the performance of reservoirs depleted by multilateral wells extending in arbitrary trajectories. The study introduces new practical solutions for estimating stabilized pseudo-steady state (PSS) productivity index and starting time of PSS as well as transient PI behavior of multilateral wells in single and dual porous media with laterally and spatially anisotropic characteristics.Several analytical models are used in this study for describing pressure and pressure derivative behavior of multilateral wells considering different reservoir configurations and types and different wellbore lengths and directions. These models are developed for laterally and spatially anisotropic reservoirs consisting of single homogenous and dual heterogeneous porous media (Naturally fractured reservoirs) and depleted by multilateral wells extending from single vertical wellbore at different horizons and directions. The models are modified to identify the staring time of PSS flow or the time when boundary dominated flow regime is developed. They are also applied to estimate the time variant transient PI and time invariant stabilized PSS PI for constant single lateral flow rate or constant vertical wellbore commingled flow rate.The outcomes of this study are summarized in: 1) Developing new analytical solutions for pressure distribution in porous media drained by multilateral wells. 2) Developing new integrated approach for estimating stabilized PSS productivity index. 3) Understanding pressure, pressure derivative, and PI behavior of finite acting reservoir depleted by multilateral horizontal wells during transient and PSS production. 4) Investigating the impacts of different reservoir configurations and types, wellbore lengths and directions, permeability anisotropy characteristics, and single and dual porous media petrophysical properties on stabilized PSS productivity index.The novel points in this study are: 1) The optimum reservoir configuration that gives the maximum stabilized PI is the rectangular shape reservoir with reservoir length to width ratio of (2−4). 2) The lateral with long wellbore and the slightly deviated from the horizontal directions gives the greatest stabilized productivity index. Stabilized PI is impacted by the length and direction of each multilateral as well as lateral wellbore location in the vertical plane. 3) Lateral reservoir anisotropy exhibits bad PI compared to the spatial anisotropy. 4) PI of conventional dual porous media reservoirs is greater than the index of unconventional reservoirs at early and late production time, but the index at intermediate production time demonstrates the greater value for unconventional reservoirs.