Pressure transient analysis of wells with horizontal drainholes: SUPRI TR-51

Technical Report · Tue Jul 01 04:00:00 EDT 1986

OSTI ID:5756265

Clonts, M D; Ramey, Jr, H J

This study presents an analytical solution for the transient pressure response of a uniform flux horizontal drainhole in an anisotropic reservoir of finite thickness. The solution also applies for a reservoir with multiple drainholes in a vertical array. The analytical solution is developed using instantaneous source functions, Green's functions and the Newman product method. The solution shows that there are two possible types of transient pressure behavior depending on the length of the drainhole relative to the height of the resevoir. If the drainhole is short, flow is characterized by three flow periods: an initial radial flow perpendicular to the drainhole axis, a transition flow period, and a pseudo-radial flow period. If the drainhole length is long relative to the reservoir height, the initial radial flow period ends instantaneously for all practial purposes. The transient pressure behavior here is identical to that of a uniform flux veritical fracture and is characterized by early time linear flow followed by a transition period and late time pseudo-radial flow. It is demonstrated that the pressure transient response for multiple drainholes is identical to the single drainhole solution if dimensionless variable are defined relaive to the number of drainholes. Consequently, the pressure response of a uniform flux vertical fracture can also be approximated by several short drainholes. The solution for infinite conductivity drainholes is also suggested by analogy to the infinite conductivity verticl fracture solution. Log-log type curves are presented for various drainhole radii and can be used in the conventional manner to determine reservoir characteristics including directional permeability or drainhole half length. Short and long time approximations are presented along with appropriate time limits. Finally, conditions for greater productivity than with vertical wells or hydraulic fractures are presented. 53 refs., 33 figs., 17 tabs.

• Research Organization: Stanford Univ., CA (USA). Petroleum Research Inst.
• DOE Contract Number: AC03-81SF11564
• OSTI ID: 5756265
• Report Number(s): DOE/SF/11564-16; SUPRI-TR-51; ON: DE86000291
• Country of Publication: United States
• Language: English

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