TAMU PETE 662 - SPE100207_slides (25 pages)

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SPE100207_slides



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SPE100207_slides

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Pages:
25
School:
Texas A&M University
Course:
Pete 662 - Production Engineering
Production Engineering Documents
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SPE 100207 The Relative Importance of Wellbore Pressure Drop and Formation Damage in Horizontal Wells A D Hill and Ding Zhu Texas A M University Background Previous studies have identified particular conditions for which wellbore pressure drop effects are important In some cases pressure drop will restrict limit or even eliminate well flow rate at the surface No quantitative general guidelines have been developed to aid well performance prediction Background Difference between vertical and horizontal multilateral wells complex trajectory of wellbore Objectives Present simple analytical expressions to determine the relative effects of wellbore pressure drop and formation damage on horizontal well inflow Use the equations to show how horizontal wells or laterals can be designed so that neither of these effects causes significant flow restrictions Concept pe pwf Dpwell affects flow rate distribution along a horizontal lateral Dpwell depends on flow rate Non uniform flow distribution Higher drawdown at the heel possibly causes early coning Approach pe Pwf i Segment wellbore Calculate reservoir flow by an inflow equation Calculate wellbore flow by a wellbore pipe flow equation Update drawdown at each segment Inflow Equation for Steady State Flow Furui et al Model 141 2qBo 0 294hI ani yb Dpr ln s sR kL rw I ani 1 hI ani z y L rw h 2yb s formation damage skin sR partial penetration skin Iani anisotropy ratio Wellbore Pressure Drop Frictional pressure drop in horizontal pipe Dpw D L 2 f u 2 L gc D u f L D flow velocity friction factor length of pipe diameter of pipe Relative Importance of Pressure Drop Wellbore pressure drop is important only when it is large relative to the reservoir pressure drop drawdown Relative Importance of Wellbore Pressure Drop Dp f Dpr NH 4 f f N Re N H kL2w yb 4 0 294hI ani D ln s sR rw I ani 1 hI ani Dpr Dpw Relative Importance of Wellbore Pressure Drop Dp f Dpr 4 f f N Re N H kL2w NH 4 0 294hI ani yb D ln s sR rw I ani 1 hI ani 4q N Re D Relative Importance of Wellbore Pressure Drop Dp f Dpr 4 f f N Re N H Dpr Dpw Important parameters Reservoir permeability Formation damage conditions Wellbore length Wellbore diameter Wellbore trajectory Relative Importance of Wellbore Pressure Drop Dp f Dpr 4 f f N Re N H Wellbore pressure drop is high when Wellbore flow rate is high high NRe Reservoir drawdown is low high NH Relative Importance of Wellbore Pressure Drop Dp f Dpr 4 f f N Re N H We have assumed that we can approximate the wellbore pressure drop by calculating the frictional pressure gradient using the average flow rate q 2 Is this good enough The Comparison of Analytical Modal with Numerical Simulation 6005 Pressure psi 6000 ouyang Yuan no inflow 5995 5990 5985 5980 5975 5970 1000 800 600 length ft 400 200 0 Relative Importance of Wellbore Pressure Drop Dp f Dpr 4 f f N Re N H High permeability Small wellbore diameter Large wellbore length Example kx Dpr q Dpratio 50 500 4630 0 01 50 1000 9270 0 02 100 500 9266 0 04 100 1000 18500 0 081 1000 50 9270 0 41 1000 100 18500 0 81 500 50 4630 0 1 500 100 9270 0 2 500 200 18500 0 4 Conditions for significant wellbore pressure drop 200 0 06 0 08 180 0 04 0 06 160 0 02 0 04 140 120 0 00 0 02 100 2000 3000 4000 5000 well length ft k md Formation damage Is it important 1 0 s 5 s 10 s 20 0 8 0 6 Jd Jo 0 4 0 2 0 0 0 0 0 2 0 4 0 6 0 8 h y b Fig 4 Effect of formation damage on horizontal well production in an isotropic reservoir 1 0 Foramtion damage effects influence of anisotropy 1 0 s 10 Iani 1 s 10 Iani 5 0 8 s 10 Iani 10 0 6 Jd Jo 0 4 0 2 0 0 0 0 0 2 0 4 0 6 0 8 1 0 h y b Fig 5 Effect of formation damage on horizontal well production in an anisotropic reservoir Conclusions The importance of the wellbore pressure drop in a horizontal well is determined by 3 dimensionless numbers The Reynold s Number for pipe flow The horizontal well number which is related to the reservoir pressure drop The friction factor for pipe flow Conclusions The pressure drop in a horizontal well can be estimated in most cases by assuming a constant pressure gradient along the well and calculating the pressure gradient using the total flow rate divided by 2 Conclusions Results show that the wellbore pressure drop is important only for long horizontal wells in high permeability formations Example input data Dp psi 1 toe Average flow rate b d 1000 2 3000 0 4 3 5000 1 1 4 7000 2 0 5 heel 9000 3 3 Segment 0 1 Example Dp psi 1 toe Average flow rate b d 1000 2 3000 0 4 3 5000 1 1 4 7000 2 0 5 heel 9000 3 3 Segment 0 1


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