Transient Dual-Porosity Behavior for Horizontal Wells Draining Heterogeneous Reservoirs

Verga, Francesca; Beretta, Enzo; Albani, D.

doi:10.2118/68844-ms

Cited by 6 publications

(2 citation statements)

References 18 publications

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“…Horizontal well intersecting a High-Permeability Streak Based on the work by Verga et al (2001), the presence of a high-permeability streak was investigated. Attempting to match real data from Well C, a 100ft-wide and 120ft-thick high-permeability streak with horizontal permeability, k H of 10, 000mD surrounded by a 10mD matrix was modeled with the horizontal well intersecting the streak at mid-point.…”

Section: Dual Layer Formation With Higher-permeability Layer Overlyinmentioning

confidence: 99%

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Bilinear Flow in Horizontal Wells in a Homogeneous Reservoir: Huntington Case Study

Feng

2015

Europec 2015

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In the Huntington field, bilinear flow with a clear one-quarter unit slope in the pressure derivative has been observed during intermediate-times in horizontal well tests, instead of the usual linear flow with a half unit slope expected in a homogeneous reservoir. This paper investigates various analytical methods with numerical methods to explain this behaviour.A number of plausible explanations of this pressure behavior were investigated in this study: rate history or production-time effects; transition between early and late time derivative radial flow stabilizations which could yield a quarter slope straight line on the derivative for specific combinations of horizontal and vertical permeabilities, well length and reservoir thickness; and geological conditions such as high-permeability streaks, the presence of shale barriers, and layering with varying permeability.It was concluded from numerical simulations and geological evidence that the most likely explanation, which yields the best match with well test data, was uniform horizontal permeability and non-uniform vertical permeability increasing from the bottom to the top of the reservoir. This is consistent with the geology of the Huntington field, where the depositional sequence is dominated by high-density turbidity currents.At each sedimentation pulse, heavier pebble/gravel lags were deposited first at the base of channels followed by finer particles which may have formed thin shale drapes. In addition, diagenesis might have led to cementation of pebble/gravel lags. The non-uniform and non-laterally extensive occurrence of the cemented pebble/gravel lags and thin shale drapes act as local baffles to vertical flow but not to horizontal flow resulting in bilinear flow behaviour in the reservoir. This paper offers a unique insight into an integrated effort at combining analytical, numerical well test models and geological evidence to explain the reservoir behavior observed in the Huntington field.

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Section: Dual Layer Formation With Higher-permeability Layer Overlyinmentioning

confidence: 99%

“…Verga et al (2001) showed that despite permeability contrasts between layers exceeding two orders of magnitude, bilinear flow could not be reproduced in a reservoir simulation. Instead, it was found that bilinear flow is formed when a high-permeability sub-vertical zone is intercepted by the horizontal well.…”

Section: Introductionmentioning

confidence: 99%

Bilinear Flow in Horizontal Wells in a Homogeneous Reservoir: Huntington Case Study

Feng

2015

Europec 2015

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Accomplishments and Challenges of Horizontal Well Technology in Hassi Messaoud Oilfield

Achi

2008

All Days

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At present, about half of Hassi Messaoud field output is being produced from hundreds of non-conventional wells. Two horizontal well (HW) applications are being used; new infill medium-radius horizontal wells in between productive zones and re-entry of dry-to-poor vertical producers all over the field using short-radius equipment. The purpose of both projects is to recover incremental oil from poor-quality reservoir parts in order to boost overall production and improve oil recovery. Horizontal well technology has proven to be a good alternative to overcome reservoir areal heterogeneity and intercept natural fractures when present in the reservoir. Although the two techniques have significantly improved production from marginal areas, several limitations and problems still have to be addressed. Challenges include weaker-than-expected productivities, rapid production decline rates in most wells, difficulties in data acquisition and inadequate completions for both remedial stimulation and zonal isolation. This study attempts to bridge production profiles with well and reservoir parameters such as; well length, permeability, vertical communication, lateral heterogeneity and anisotropy, near wellbore damage, pressure support,…etc. The article presents a comprehensive analysis of horizontal wells in the field and investigates many aspects of the observed success and failure cases. It also discusses the benefits of underbalanced drilling and pre-perforated liner completions. By benchmarking current well performances, the paper draws some suggestions for well design and completion strategies for prospective wells. Introduction The Hassi Messaoud reservoir has been on stream since 1958. Currently, it produces about 65 Mm3/D of 45°API oil from a thick Cambro-Ordovician sandstone formation. The structure is a flattened anticline with a sequence of horts and grabbens contained by faults in a submeridian direction. The faults are generally oriented SSW to NNE and cross the entire reservoir. The depositional environment is fluvial at the bottom to marine at the top. The shaly sandstone contains silt interbeds which have a thickness between 0.2 and 0.4 m with a metric to kilometric lateral extension. The reservoir is naturally fractured in some parts because of tectonic activity. Fractures are either open or plugged with materials such as shale, silica, anhydrite, pyrite, and bitumen. The reservoir is subdivided into four distinct formations—Ri, Ra, R2, and R3—in addition to a zone of alternance with Ra-Ri and R2 being the main and secondary reservoirs respectively. The producing Ra-Ri is subdivided into six intervals: D5, D4, D3, D2, ID, and D1. The reservoir has a porosity ranging from 6 to 12 %. Overall, the permeability is low with a range from less than 1 to more than 100 md in open-fissures layers. The reservoir was initially undersaturated with an oil saturation of about 80%. The reservoir was subdivided into productive zones. Most zones are under miscible gas flooding. Five zones are under water injection. Up until 1995, the reservoir was developed using vertical wells. Along with matrix treatments, hydraulic fracturing is extensively used with more than 300 wells already treated to compensate for low permeability or to bypass nearby wellbore damage. Gaslift is used for production activation throughout the field. Pilot projects for horizontal well technology started in the mid 1990s. The objective was to develop the reservoir's areas where conventional vertical drilling deemed unsuccessful. The first application was drilling medium-radius infill wells in lower permeability areas and at the peripheries of zones where heterogeneities are high and reservoir continuity is uncertain. The second technique consisted of re-entering dry-to-poor vertical wells using short radius drilling equipment. In this study we discuss the implementation, lessons learned and challenges of these unconventional wells. Many reservoir and production aspects are also discussed throughout the paper.

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Transient Pressure Analysis of Horizontal Wells in a Multi-Boundary System

Rbeawi

Tiab

2011

SPE Production and Operations Symposium

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Horizontal wells can greatly increase the contact area of the wellbore and the pay zone; so they are commonly applied in oil reservoirs to enhance the production and ultimate recovery, especially in low permeability formations. The purpose of this study is to develop a technique for the interpretation of transient pressure based on dimensionless pressure and pressure derivative. Type curve matching is one of the techniques that can be used to interpret the pressure data of horizontal wells in finite reservoirs. Starting from very short horizontal wells to extra-long wells, the pressure behavior of the wells has been analyzed for different conditions. The effect of the outer boundaries of the reservoir on the pressure behavior of the horizontal wells has been investigated for different configurations. Rectangular shape reservoirs with different dimensions have been used to study the pressure response in the well. Five flow regimes have been observed for regular length horizontal wells; early radial, early linear flow, pseudo radial flow, channel flow or late linear flow, and pseudo-steady state flow. While only four flow regimes have been observed for the extra-long wells; linear flow, pseudo radial flow, channel flow, and pseudo-steady state or boundary affected flow. Of course, those flow regimes do not always take place under all conditions. Pseudo-steady state flow is expected to occur after long producing time. A pressure drawdown test was solved using the proposed type curve matching technique. The study has shown that the effect of the boundary on the pressure response of the horizontal wells and the type of flow regimes depend on the length of the horizontal wells and the distance to the nearest boundary.

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Transient Dual-Porosity Behavior for Horizontal Wells Draining Heterogeneous Reservoirs

Cited by 6 publications

References 18 publications

Bilinear Flow in Horizontal Wells in a Homogeneous Reservoir: Huntington Case Study

Bilinear Flow in Horizontal Wells in a Homogeneous Reservoir: Huntington Case Study

Accomplishments and Challenges of Horizontal Well Technology in Hassi Messaoud Oilfield

Transient Pressure Analysis of Horizontal Wells in a Multi-Boundary System

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