The document discusses the effect of partial penetration in well testing. When a well is perforated over less than the total thickness of the producing zone, the pressure drop near the wellbore is increased. This results in a more positive apparent skin factor. The skin factor is the sum of the skin caused by formation damage and the skin caused by an incomplete perforated interval. The example given is of a well perforated over only 10 feet of a 50 foot thick formation, which would result in a more positive skin factor due to the partial penetration.
analog-vs-digital-communication (concept of analog and digital).pptx
Effect of partial penetration
1. EFFECT OF PARTIAL
PENETRATION
IN WELL TESTING
N A M E : K R I PA L R . PAT E L
R O L L N O. : 1 7 B P E 0 7 4
S U B J E C T : W E L L T E S T A N A LY S I S
2. INTRODUCTION
• In the case of partial penetration, the well
communicates with only a fraction of the
producing zone thickness.
• When a gas cap or bottom water drive is
active at the upper or lower boundary, the
well being perforated as far away as
possible from the constant pressure
surface.
3. • When the completed interval is less then total formation thickness, the pressure drop
near the wellbore increased and the apparent skin factor becomes increasingly positive.
• Total skin determine from
Where,
Sd= Skin caused by formation damage
Sp= Skin caused by an incomplete perforated interval
5. • Flow Regimes :
1.) Near well bore – Radial
2.) Slightly away from well bore – Spherical
3.) At a distance – Radial
6.
7.
8. EXAMPLE
A well with disappointing productivity is perforated in 10 ft of a total formation thickness
of 50 ft. Vertical and horizontal permeabilities are believed to be equal. A pressure
buildup test was run on the wall; result and basic properties are summarized as follows:
