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Chapter 16

Horizontal Well Testing

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Useful References Kuchuk, F., Goode, P.A., Brice, B.W., Shrerrard, D.W., Thambynayagam,

Pressure-Transient Analysis for Horizontal Wells, JPT, Aug 1990, 1022-1030(paper SPE 18300).

Odeh, A.S., and Babu, D.K.: Transient Flow Behavior of Horizontal Wells:Pressure Drawdown, and Buildup Analysis, SPEFE March 1990, 7-15.

Odeh, A.S., and Babu, D.K.: Productivity of a Horizontal Well, SPERE Nov.1989, 417-421.

Abbaszadeh M and He eman P S : Pressure-Transient Anal sis for a Slanted

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, . , . . i l i lWell in a Reservoir With Vertical Pressure Support,SPEFE (September 1990)277.

Kuchuk, F., Goode, P.A., Wilkinson, Thambynayagam, R.K.M.: Pressure-Transient Behavior of Horizontal Wells With and W ithout Gas Cap or Aquifer,SPEFE, March 1991, 86-94 (paper SPE 17413).

Kuchuk, F., and Habashy, T.: Pressure Behavior of Horizontal Wells in MultilayerReservoirs With Crossflow, SPEFE, March 1996, 55-66.

Thompson, L.G., and Temeng, K.O., Automatic Type-Curve Matching forHorizontal Wells, paper SPE 25507, March 1993.

Useful References

Onur, M., Hegeman, P.S., and Kuchuk, F.J.: Pressure-Transient Analysis ofDual Packer-Probe Wireline Formation Testers in Slanted Wells, paper SPE90250 presented at the SPE Annual Technical Conference and Exhibition held inHouston, Texas, U.S.A., 2629 September 2004.

Ozkan, E.: Analysis of Horizontal-Well Responses: Contemporary vs.Conventional, SPEREE, Aug 2001, 260-269.

Sada, D.J.: Horizontal Well Technology, PennWell Publishing Co. Tulsa, OK.,

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1991.

Bourdet, D.: Well Test Analysis: The Use of Advanced Interpretation Models,Elsevier Science B.V., Amsterdam, The Nethelands, 2002.

Horne, R.: Modern Well Test Analysis-A Computer-Aided Approach, SecondEdition, Petroway, Inc., Palo Alto (1995).

Modern Reservoir Testing, Schlumberger publication, Houston, TX, 1994.

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Introduction

Since 1980s, horizontal wells have been extremely popular. The major

purpose is to enhance reservoir contact and hence well productivity.

In general, a horizontal well is drilled parallel to the reservoir bedding plane

(see below figure w = 90o), while a vertical well is drilled perpendicular tothe bedding plane (w = 0o). The wells intersecting the bedding plane withan angle w different from 0 to 90o are called slanted (or deviated) wells.

4y

z

z w

w

z

h

(x,y,z)

rw

x

Introduction (Contd)

The increase in the applications of horizontal (and also slanted)wells has brought an impetus development of the procedures to

evaluate the performances and productivity of horizontal wells.

Here, we will focus only on the interpretation of pressure transient

measurements from horizontal wells to be able to determine

formation parameters that control performance and productivity of

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horizontal wells.

However, I should note that interpretation of pressure transients ismuch more difficult than interpretation of those from vertical wells:

3D nature of the flow geometry (so many parameters affecting the pressure

behavior of the horizontal well; This makes the application of classicalconventioal analysis methods very difficult. Non linear regression seems to be

the most useful)

Introduction (Contd)

Considerable wellbore storage effects (this mask critical reservoir flowregimes, e.g., early-radial flow governed by the vertical permeability of

the reservoir. Deconvolution can be useful to eliminate wellbore

storage effects, but requires accurate measurements of sandfacerates, although there are wellbore storage deconvolution methods not

requiring sandface rate measurements which assume that a constant

wellbore storage model is adequate to represent the wellbore storage

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.

Wellbore haydraulic (conductivity of the wellbore is in general finite).

Non uniform skin effect along the wellbore.

Selective completions along the horizontal well.

Heterogeneities in vertical direction as well as lateral directions.

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Pressure Transient Behavior of a

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Basic Flow RegimesInfinite System in

the x-y Plane

zx y

kxkykz

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y z wk k L

y t wk c L h

Early (or Vertical) radial flowdue to convergence of flow

only in the vertical (y-z) planenormal to the well axis.

Slope of p vs. lnt controlled by Intermediate-time linear flowregime (occurs if Lw >> h)

Slope of p vs. sqrt(t) controlledby

Late (or Horizontal) radial flow

(some people referred to aspseudo-radial flow).

Slope of p vs. lnt controlled by

x yk k h

On Anisotropic Permeability

If we define principal directions of permeability as kx, ky ( inx-yplane) and kz (z is the vertical direction), then

(3D anistotropic reservoir).

(isotropic in the x-y plane, but

zyx kkk

)(, vhvzhyx kkkkkkk ===

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anisotropic in the z-direction)

For vertical wells, the radial flow is governed by the horizontalpermeability,

For horizontal wells, early radial flow is governed by the geometricmean of kh and kv, while late-radial flow is governed by horizontalpermeability, only.

( )h x yk k k=

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On Anisotropic Skin Factor If we have anisotropy in permeability in the horizontal and/or

vertical plane, this causes our well to be an ellipse in theequivalent isotropic system, and this appear as skin effect

on pressure.

well

Horizontal/Vertical plane

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kmin

kmax

+=

2

44minmaxmaxmin

ww rr

02

//ln

44