effects of fracture geometry on well productivity
DESCRIPTION
Project on Hydraulic Fracturing at Univ of Wyoming for production engineering class.TRANSCRIPT
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Effects of Fracture Geometry On Well Productivity
PETE 3715Tuesday 4/22/2014
Group Members: •Alan Alexeyev•Ahmed Mohamed•Aziz Al-Umairy•Pradyumn Singh
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Components of Fracture Geometry and determining factors.
• Parameters:•Half Length (Xf )•Fracture Width (w)•Fracture Height (hf)•Fracture Conductivity ( CfD)•Proppant Number (Np)
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Introduction • The hydraulic fracture design is highly dependent on
reservoir permeability
• What fracturing accomplishes is to alter the way fluids enter the wellbore . It changes the flow from near well radial flow to linear or bilinear flow.
• Optimal levels of fracture dimensions are needed for maximizing the productivity index which Proppant Number and conductivity.
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•Generally for higher permeability reservoirs , a large Fracture width is necessary for optimal production. Height and length are of secondary importance.
•For lower permeability reservoirs , fracture permeability , width and height are of secondary importance. Length of the fracture is given more importance.
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PKN & GDK Models
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There are two models which help us to determine the fracture Geometry :
PKN : This option is most applicable for fractures with length to height aspect ratios less than unity or for fractures which display slip at the upper and lower boundaries. λ= 2L/H < 1 Figure 1. PKN model.
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GDK : This option is most applicable for fractures with length to height aspect ratios less than unity or for fractures which display slip at the upper and lower boundaries. λ= 2L/H < 1
• Figure 2.GDK Model.
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Length and Conductivity of Fractures
•Every hydraulic Fracture can be characterized by its length, conductivity and skin effect. However , we are going to take skin effect as zero throughout the presentation.
Relative capacity , a = k= permeability half length kf = fracture permeability w= fracture width
•Relative Capacity is important because smaller values of relative capacity implies large fracture permeability-width product and thus a high conductivity fracture.
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•Conductivity •
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Figure 17.4
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Fracture Width •It is the horizontal length of the propped fracture.
•Formula
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Figure 17.4
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Figure 17.9
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Figure 17.8
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How Fracture Geometry Effects Production
Productivity Index •Until the optimal level of width and half length ,
Productivity index keeps increasing. Optimal level of conductivity is 1.6 .
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Example: Calculation of the optimal fracture dimensions and maximum pss Productivity Index in the oil well.
Given Data: k = 15 mdBo= 1.1 rsb/stbμ= 1 cpMass of proppant (Mp) = 150,000 lbProppant specific gravity = 2.65Φ(Porosity) = 0.38Kf = 60000mdh(reservoir) = 50ft h(fracture) = 100ftArea = 4*106 sq.ft.
Find optimal dimensions, pseudosteady-state productivity index and folds of increase from fracturing.
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Example: Calculation of Fracture Width and Length with a Newtonian Fluid using PKN Model
Find maximum and average fracture widths when fracture half length is 500 ft. μapparent=100cp, injection rate qi=40bpm. Poisson ratio v= 0.25E=4*10^6hf=100ftxf=1000ft