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Российский государственный университет нефти и газа им. И.М. Губкина

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Part II - Well completion design.pdf

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Erosion risk management

Examples of developing materials with improved erosion resistance

Choice of correct material in critical wear parts can increase the life by a factor of 10100.

	100		140
rateErosion[mm3/kg]			120
rateErosion[mm3/kg]	10			Hardness/ Toughness
			100		WS 90/90
	1		80		WS 90/30
	1		60		Hardness
			60		Hardness
			40		Toughness
	0,1		40
	0,1
			20
	0,01Stainless	Traditional	0
	steel 316L	Traditional	Improved TC-
	steel 316L	TC-material	material

Part II - Well completion design

Sand management

Focus areas

 High quality data acquisition

Sand production prediction to evaluate need for sand control

Open hole solution for sand control to limit production impairment

Erosion risk management

Top side sand handling and disposal according to regulations

Part II - Well completion design

Gravel packing

Part II - Well completion design

Gravel packing

Part II - Well completion design

Gravel packing

Part II - Well completion design

Gravel packing

Mesh = number of openings per inch, counting from the center of any wire in the sieve to a point exactly 1 inch distant. Mesh sizes are read as follows: 20/40 mesh commercial gravel passes through a 20-mesh sieve and is retained by a 40-mesh sieve.

20/40 commercial gravel has permeability kg approx 120 D and bg = 30000 1/ft

Part II - Well completion design

Gravel packing

Productivity of a well:

qo =

2πkh∆p

µo Bo ln r

+Stot

Total skin:

Stot

=...+

S gp

+Dgp qo

Linear term:

S gp =.

2πklgp

kgp

ns Ap

Non-linear term: Dgp =1.80 10−11 Bo ρokhlgp βg

µod p 4n2

Part II - Well completion design

Gravel packing

According to the Forcheimer equation the high velocity flow effect can be calculated as follows:

for gas wells:

D gp = 2.45 10−13			γ g khL p	βg
D gp = 2.45 10−13			µg d p 4n2	βg
			µg d p 4n2
for oil wells:
D gp =1.80	10	−11	Bo ρokhL p	βg
D gp =1.80	10		µod p 4n2	βg
			µod p 4n2

Part II - Well completion design

Gravel packing

Evaluation of βg-values

Cooke (1973):	βg =b kg −a
Geertsma (1974):
dry gravel:	βg =1.746 107 k g −0.5 φ−1.5
wet gravel:	βg =	1.746 107	kg +0.5 φ−1.5
wet gravel:	βg =	krg 0.5	(1−Sw )1.5
		krg 0.5	(1−Sw )1.5
Jones and Owens (1980):	β = 0.86 kl −0.33
Zolotukhin (2001):	β = λ2/3 φ1/3 kl −1/3

λ – free pass of gas molecules at standard conditions

Part II - Well completion design

Gravel packing

The essentials involved in designing the gravel flow pack are:

Analyzing the production formation

Assertaining the gravel-to-sand ratio

Determining formation sand uniformity, and

Estimating the velocity through the slots

Part II - Well completion design

Gravel packing

Sieve analysis of the formation sand and grain size distribution

Sand grain size distribution

100

Cumulative distribution, %

0.1

0.01

0.001

Grain size (diameter), in

Part II - Well completion design

Design of gravel pack

Analysis of producing formation

−For correct gravel sizing, the producing formation’s grain size must be determined accurately!

−A representative sample is extracted, dried, weighed, separated and passed through screens of varying sizes, from the largest to the smallest screen.

−The material on each screen is weighed and a plot of the grain size distribution is constructed

Part II - Well completion design

Design of gravel pack

Analysis of producing formation (cont-d)

−The slope of the curve is a measure of the sand’s uniformity.

−A uniformity coefficient C is determined from the

following equation: C=d40/d90, where d40 is the grain diameter at 40 percentile point and d90 – at 90 percentile point

−C<3 describes a uniform sand

−C>5 – a non-uniform sand

Part II - Well completion design

Design of gravel pack

Gravel-to-sand ratio (GSR) – a ratio of the gravel grain

size to the formation grain size

−GSR < 4 produce a table pack but impairs productivity

−GSR > 10 – formation invades the pack and reduce permeability

−GSR of 5-6 is optimal (Cgp = 1.5 – 2)

Grain selection

−Quality for gravel: roundness and sphericity > 0.7

Gravel pack thickness

−The ideal GP thickness is not less than 6 inches

Part II - Well completion design

Design of gravel pack

Example of uniform and non-uniform grain size distributions

Ca=0.008/0.004 = 2; Cb = 0.008/0.002 = 4

Part II - Well completion design

Design of gravel pack

Sand uniformity coefficient

C= d40 d90

A C ratio less than 3 describes a uniform sand while a C ratio greater than 5 describes a non-uniform sand

Part II - Well completion design

Design of gravel pack

Gravel-to-Sand ratio:

GSR = D50

d50

Gravel-to-Sand ratio is the most important parameter used to design a gravel flow pack

GSR should be > 4 and < 10

An optimum value GSR = 6

Part II - Well completion design

Design of gravel pack

Cumulative distribution, %

Sand grain and gravel size distribution

100

0.1

0.01

0.001

Grain size (diameter), in

Part II - Well completion design

Gravel Selection

Sphericity

0.9

0.7

0.5

0.3

0.1

0.3

0.5

0.7

0.9

Roundness

Part II - Well completion design

Gravel packing

Vertical well with installed tools for gravel packing

Crossover

packer

Screen

Wash pipe

Part II - Well completion design

Gravel packing

Flow paths and the packing sequence in a vertical well

Part II - Well completion design

Gravel packing

450

Flow paths and the sequence in a deviated

Part II - Well completion design

Gravel packing

Flow paths and the packing sequence in a high angle deviated or horizontal well.

The numbers show the order of gravel pack placement. Numbers from 1 to 7 correspond to the alpha-wave, while numbers from 8 to 11 indicate the beta-wave.

Part II - Well completion design