Case histories

Optimizing stage spacing in a vertical well

01 Jul 2014

Well data

Location
  • Utah, USA, Dolomite sand
Well Type
  • 7-stage vertical well, 4 with CARBONRT
Proppant
  • CARBONRT LITE 20/40, 535 klb total in 4 stages
  • CARBOLITE 20/40, 382 klb total in 3 stages
  • CARBONRT stages alternated with CARBOLITE stages to determine if the propped fractures grew out of zone
Well Conditions
  • 10,500 - 12,400 ft MD
  • 0.90 psi/ft fracture gradient
  • 240°F BHT

CARBONRT helps determine if fractures are growing past packers

Challenge:

The operator was looking for a way to optimize stage spacing in their fracture treatment design with a primary concern that fractures were growing past packers.

Solution:

CARBO alternated between CARBONRT (with its non-radioactive tracer) and CARBOLITE to create contrast between stages. If CARBONRT was detected in the non-NRT stages, it was determined that the NRT fractures had grown past the packers.

Stages 1, 3, 5 and 7 used CARBONRT with stages 2, 4 and 6 using CARBOLITE without NRT. This allowed for three situations to indicate if propped fractures were growing vertically out of the intended zone and three situations to determine if propped fractures were growing downward past the plug.

Value:

The client was able to trace the CARBONRT and determine that in none of the situations did the propped fractures grow excessively vertically and into the next stage’s area. Excessive growth down past the packer did occur in stage 5, resulting in 8 ft of propped fracture growth into the stage 4 area. Stage 3 had minor growth downward past the packer into the stage 2 area. Stage 7 was fully contained, with no growth past the packer.

Article396-Chart1.png

Fracture was contained in stage 7; 141 ft total stage frac
height.

Article396-Chart2.png

About 8 ft of propped frac height bypassed packer into
stage 4; 110 ft total stage frac height.

Author(s): Mark Chapman

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