Analysis of Development Methods for Gravel Envelope Wells   -   i

Summary

Five basic techniques of well development have been studied. The purpose of the investigation was to provide a quantitative basis for evaluating the relative efficiency of respective development methods in gravel envelope wells. The techniques evaluated were:

  • jetting
  • line swabbing
  • rocker beam swabbing
  • single swab mounted on drill pipe with simultaneous injection below the swab
  • double swabs mounted on drill pipe with injection between the swabs

The analysis assumed a completed well with a filter pack between the screen and the aquifer. The primary goal of the studies performed was determination of the direction and magnitude of the flow velocity field at the pack/ formation interface. Evaluation of this flow velocity distribution gives clear indication of the ability of the development techniques to clean drilling debris and wall cake from the formation.

Results of the study indicate that both swabbing and jetting can be effective development mehods for gravel envelope wells. Swabbing methods involving pumping appear to offer even further benefits. The efficiency of jetting techniques is found to be conditional on use of a filter pack size distribution that will enable filter particle circulation to develop. In the absence of this circulation, jetting is likely to be of limited use.


Symbol Table

a well screen radius (ft)
b borehole radius (ft)
c jet radius (ins)
D distance from swab to well bottom (ft)
g gravitational acceleration (ft/sec2)
h1 head loss across leaking swab (ft H2O)
H head differences across a swab (ft H2O)
k1 hydraulic conductivity of filter pack (gpd/ ft2)
k2 hydraulic conductivity of formation (gpd/ ft2)
2L swab spacing with double swabs (ft)
Q injection flow rate (gpm)
R dimensionless parameter  
S specific storativity (ft-1)
t time (sec)
T thickness of filter pack (ins)
U velocity of moving swab (ft/ sec)
ve tangential velocity of radius b, double flange swab (ft/ sec)
vj jet velocity (ft/ sec)
vo scaling velocity for double flange swab (ft/ sec)
vr radial velocity of radius b (ft/ sec)
v* scaling velocity for single flange swabbing (ft/ sec)
V discharge velocity through leaking swab (ft/ sec)
z distance from swab along well axis (ft)
pi = 3.141593

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