Effects of Pressure Drop in Horizontal Wells and Optimum Well Length

Finding the breakthrough position of horizontal wells is essential to water plugging and improving oil production in bottom water drive reservoirs. Physical modeling was carried out in this paper to research the law of bottom water’s movement. The experimental results indicated that: pressure drop in wells, well trajectory and area reservoir heterogeneity were all sensitive factors for breakthrough of bottom water, and the entry points of horizontal wells were determined by the combined function of them. In different well trajectory models, the concave down part of the well cooperate with pressure drop influenced the breakthrough position. Bottom water below the heel end reached the well earliest if the concave down part located at the heel end. When the concave part located at the middle of the well, the two factors played role respectively which resulted in breaking through of bottom water at two places with larger swept area. In different heterogeneous models, permeability difference and pressure drop were both favorable factors for bottom water’s non-uniformly rise. In the model that the heel end located at high permeability part, bottom water under the heel end reached the well earliest. If the heel end was set at the low permeability part, the breakthrough of bottom water occurred at the middle of the well.

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Can We Engineer Better Multistage Horizontal Completions? Evidence of the Importance of Near-wellbore Fracture Geometry from Theory, Lab and Field Experiments

10.2118/spe-173363-ms ◽

2015 ◽

Author(s):

B.. Lecampion ◽

J.. Desroches ◽

X.. Weng ◽

J.. Burghardt ◽

J.E.. E. Brown

Keyword(s):

Pressure Drop ◽

Field Experiments ◽

Horizontal Wells ◽

Fracture Plane ◽

Hydraulic Fractures ◽

Multiple Fractures ◽

Fracture Geometry ◽

Complex Fracture ◽

Limited Entry ◽

The Impact

Abstract There is accepted evidence that multistage fracturing of horizontal wells in shale reservoirs results in significant production variation from perforation cluster to perforation cluster. Typically, between 30 and 40% of the clusters do not significantly contribute to production while the majority of the production comes from only 20 to 30% of the clusters. Based on numerical modeling, laboratory and field experiments, we investigate the process of simultaneously initiating and propagating several hydraulic fractures. In particular, we clarify the interplay between the impact of perforation friction and stress shadow on the stability of the propagation of multiple fractures. We show that a sufficiently large perforation pressure drop (limited entry) can counteract the stress interference between different growing fractures. We also discuss the robustness of the current design practices (cluster location, limited entry) in the presence of characterized stress heterogeneities. Laboratory experiments highlight the complexity of the fracture geometry in the near-wellbore region. Such complex fracture path results from local stress perturbations around the well and the perforations, as well as the rock fabric. The fracture complexity (i.e., the merging of multiple fractures and the reorientation towards the preferred far-field fracture plane) induces a strong nonlinear pressure drop on a scale of a few meters. Single entry field experiments in horizontal wells show that this near-wellbore effect is larger in magnitude than perforation friction and is highly variable between clusters, without being predictable. Through a combination of field measurements and modeling, we show that such variability results in a very heterogeneous slurry rate distribution; and therefore, proppant intake between clusters during a stage, even in the presence of limited entry techniques. We also note that the estimated distribution of proppant intake between clusters appears similar to published production log data. We conclude that understanding and accounting for the complex fracture geometry in the near-wellbore is an important missing link to better engineer horizontal well multistage completions.

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Best Practices in DFIT Interpretation: Comparative Analysis of 62 DFITs from Nine Different Shale Plays

10.2118/205297-ms ◽

2022 ◽

Author(s):

Mark Mcclure ◽

Garrett Fowler ◽

Matteo Picone

Keyword(s):

Pressure Drop ◽

Pore Pressure ◽

Time Pressure ◽

Early Time ◽

Horizontal Wells ◽

Late Time ◽

Fracture Length ◽

Well Spacing ◽

Net Pressure ◽

The Difference

Abstract In URTeC-123-2019, a group of operators and service companies presented a step-by-step procedure for interpretation of diagnostic fracture injection tests (DFITs). The procedure has now been applied on a wide variety of data across North and South America. This paper statistically summarizes results from 62 of these DFITs, contributed by ten operators spanning nine different shale plays. URTeC-123-2019 made several novel claims, which are tested and validated in this paper. We find that: (1) a ‘compliance method’ closure signature is apparent in the significant majority of DFITs; (2) in horizontal wells, early time pressure drop due to near-wellbore/midfield tortuosity is substantial and varies greatly, from 500 to 6000+ psi; (3) in vertical wells, early-time pressure drop is far weaker; this supports the interpretation that early- time pressure drop in horizontal wells is caused by near-wellbore/midfield tortuosity from transverse fracture propagation; (4) the (not recommended) tangent method of estimating closure yields Shmin estimates that are 100-1000+ psi lower than the estimate from the (recommended) compliance method; the implied net pressure values are 2.5x higher on average and up to 5-6x higher; (5) as predicted by theory, the difference between the tangent and compliance stress and net pressure estimates increases in formations with greater difference between Shmin and pore pressure; (6) the h-function and G-function methods allow permeability to be estimated from truncated data that never reaches late-time impulse flow; comparison shows that they give results that are close to the permeability estimates from impulse linear flow; (7) false radial flow signatures occur in the significant majority of gas shale DFITs, and are rare in oil shale DFITs; (8) if false radial signatures are used to estimate permeability, they tend to overestimate permeability, often by 100x or more; (9) the holistic-method permeability correlation overestimates permeability by 10-1000x; (10) in tests that do not reach late-time impulse transients, it is reasonable to make an approximate pore pressure estimate by extrapolating the pressure from the peak in t*dP/dt using a scaling of t^(-1/2) in oil shales and t^(3/4) in gas shales. The findings have direct practical implications for operators. Accurate permeability estimates are needed for calculating effective fracture length and for optimizing well spacing and frac design. Accurate stress estimation is fundamental to hydraulic fracture design and other geomechanics applications.

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A Numerical Model for Investigating the Steam Conformance along the Dual-String Horizontal Wells in SAGD Operations

Energies ◽

10.3390/en13153981 ◽

2020 ◽

Vol 13 (15) ◽

pp. 3981

Author(s):

Peng Li ◽

Yanyu Zhang ◽

Xiaofei Sun ◽

Huijuan Chen ◽

Yang Liu

Keyword(s):

Pressure Drop ◽

Horizontal Wells ◽

Pressure Profile ◽

Steam Injection ◽

Steam Pressure ◽

Optimization Method ◽

Injection Time ◽

Reservoir Model ◽

Landing Position ◽

Steam Chamber

Non-uniformity of the steam-assisted gravity drainage (SAGD) steam chamber significantly decreases the development of heavy oil reservoirs. In this study, to investigate the steam conformance in SAGD operations, a wellbore model is developed for fluid flow in dual-string horizontal wells. Then, a three-dimensional, three-phase reservoir model is presented. Next, the coupled wellbore and reservoir model is solved with a fully implicit finite difference method. Finally, the effects of the injector wellbore configuration, steam injection ratio and injection time on the steam conformance are investigated. The results indicate that under different injector wellbore configurations, the closer the differences between the pressure drop from the landing position of the short string to the heel of the wellbore and the pressure drop from the landing position of the short string to the toe of the wellbore, the better is the steam conformance. The smaller the difference in the steam injection rate between the long and short injection strings, the higher is the uniformity of the steam chamber. The injector annular pressure profile uniformity is consistent with the steam conformance. Creating a more uniform steam pressure in the annulus of the injector improves the uniformity of the steam chamber. The steam conformance decreases with increasing injection time, so the optimization method of steam chamber uniformity should be adjusted according to different injection times.

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A Semianalytical Model for Horizontal-Well Productivity With Pressure Drop Along the Wellbore

SPE Journal ◽

10.2118/189973-pa ◽

2018 ◽

Vol 23 (05) ◽

pp. 1603-1614 ◽

Cited By ~ 4

Author(s):

Wanjing Luo ◽

Changfu Tang ◽

Yin Feng

Keyword(s):

Reynolds Number ◽

Fluid Flow ◽

Pressure Drop ◽

Horizontal Well ◽

Horizontal Wells ◽

Productivity Index ◽

Type Curves ◽

Penetration Ratio ◽

New Type ◽

The One

Summary This study aims to develop a semianalytical model to calculate the productivity index (PI) of a horizontal well with pressure drop along the wellbore. It has been indicated that by introducing novel definitions of horizontal-well permeability and conductivity, the equation of fluid flow along a horizontal well with pressure drop has the same form as the one for fluid flow in a varying-conductivity fracture. Thus, the varying-conductivity-fracture model and PI model can be used to obtain the PI of a horizontal well. Results indicate that the PI of a horizontal well depends on the interaction between horizontal-well conductivity, penetration ratio, and Reynolds number. New type curves of the penetration ratios with various combinations of parameters have been presented. A complete-penetration zone and a partial-penetration zone can be identified on the type curves. Based on the type curves, two examples have also been presented to illustrate the advantages of this work in optimizing parameters of horizontal wells.

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The Experimental and Model Study on Variable Mass Flow for Horizontal Wells With Perforated Completion

Journal of Energy Resources Technology ◽

10.1115/1.4037026 ◽

2017 ◽

Vol 139 (6) ◽

Cited By ~ 2

Author(s):

Wei Jianguang ◽

Lin Xuesong ◽

Liu Xuemei ◽

Ma Yuanyuan

Keyword(s):

Pressure Drop ◽

Mass Flow ◽

Variable Mass ◽

Axial Flow ◽

Horizontal Wells ◽

Calculation Model ◽

Frictional Pressure Drop ◽

Model Study ◽

Fluid Boundary ◽

Variable Mass Flow

The variable mass flow in perforated horizontal wells is very complex. One reason is that the perforation can increase the roughness of the pipe wall which will increase the frictional pressure drop. The other is the fluid boundary layer and velocity profile of axial flow will be changed due to the “mixing” of the inflow with the axial flow. The influences of the perforation parameters and flux rate on the pressure drawdown in horizontal wellbore are investigated. The perforation parameters include perforation phasing, perforation diameter, and perforation density. According to the experiment results, some modes such as friction factor calculation model (the accuracy of the model is 4%), “mixing” pressure drop calculation model (the accuracy of the model is 3%), and total pressure drop calculation model (the accuracy of the model is 2%) are developed.

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Effects of Formation Damage and High- Velocity Flow on the Productivity of Perforated Horizontal Wells

SPE Reservoir Evaluation & Engineering ◽

10.2118/77534-pa ◽

2005 ◽

Vol 8 (04) ◽

pp. 315-324 ◽

Cited By ~ 10

Author(s):

Yula Tang ◽

Turhan Yildiz ◽

Erdal Ozkan ◽

Mohan G. Kelkar

Keyword(s):

Pressure Drop ◽

High Velocity ◽

Horizontal Wells ◽

Formation Damage ◽

Gas Wells ◽

Skin Factor ◽

High Velocity Flow ◽

Additional Pressure ◽

Velocity Flow ◽

The Individual

Summary A comprehensive semianalytical model has been built to investigate the effects of drilling and perforating damage and high-velocity flow on the performance of perforated horizontal wells. The model incorporates the additional pressure drop caused by formation damage and high-velocity flow into a semianalytical coupled wellbore/reservoir model. The reservoir model considers the details of flow in the vicinity of the wellbore, including 3Dconvergent flow into individual perforations, flow through the damaged zone around the wellbore and the crushed zone around the perforation tunnels, and non-Darcy flow in the near-wellbore region. The wellbore flow model includes the effect of frictional pressure drop. Both oil and gas wells are considered. The expressions provided in this paper for additional pressure losses caused by perforating damage, drilling damage, and high-velocity flow can be used to optimize perforating parameters and decompose the total skin into its components (perforation pseudoskin, damage skin, and non-Darcy skin). Introduction The performance of oil and gas wells may be influenced by the simultaneous effect of mechanical skin, high-velocity (non-Darcy) skin, and completion pseudoskin factors. The skin factors caused by formation damage and perforating damage constitute the mechanical-skin factor. The extra pressure drop caused by high-velocity flow is known as the rate-dependent or non-Darcy flow factor. Compared to an ideal open hole, the wells with completions and other geometries such as perforations, slotted liner, or partial penetration may experience additional pressure loss or gain. The additional pressure change caused by wellcompletion and geometry is quantified in terms of pseudoskin factor. The combined effects of all the skin factors lead to a total skin factor that maybe estimated from pressure-transient data. The total skin factor, however, is not simply the sum of the individual skin components, and the computation of the individual skin components is not straightforward (the interaction between the individual components of total skin is nonlinear). Many studies have concentrated on the effects of formation damage and high-velocity (non-Darcy) flow on well performance. For perforated vertical wells, McLeod's analytical model has been a widely accepted approximation to account for the additional pressure drop caused by formation damage and high-velocity flow. Karakas and Tariq presented a semianalytical model to predict the pseudoskin and productivity of perforated vertical wells with formation damage. The models suggested by McLeod and Tariq, however, may not work for selectively completed wells in which the flux distribution may be nonuniform. An example of this case is selectively perforated horizontal wells. Tang et al. presented models for horizontal wells completed with slottedliners or perforations. The additional pressure drop in the vicinity of the wellbore because of formation damage, perforating, flow convergence, and high-velocity flow was included in their models in the form of a total-skinterm. The existing horizontal-well models are not capable of explicitly relating the skin factor to the physical parameters controlling the additional pressure drop around the wellbore. In addition, the interplay between the skin and flux distribution and its impact on the productivity of perforated horizontal wells have not been discussed, especially for selectively perforated horizontal wells. Non-Darcy flow effect in perforated horizontal wells is another topic that has not been addressed adequately in the literature. In this study, we present a semianalytical model to predict the productivity of perforated horizontal wells under the influence of formation damage, perforating damage, and high-velocity flow. The nonlinear interaction between the individual skin components is accurately represented in the model. The model is applicable to both single-phase oil and gas wells (the pseudo pressure concept is used to extend the oil-flow model to the gas wells). Using the model, the combined effects of formation damage, the crushed zone around the perforation tunnels, and the high-velocity flow on the horizontal-well performance have been investigated in detail. The completion and damage parameters controlling the well productivity were identified through sensitivity studies.

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