Acid Stimulation Case Study 

 Well type and location:

Vertical wells in Mississippi limestone in the Cherokee Basin, Kansas.

 Scenario:

The operator conducted 3 acid-stimulation treatments in which 5% HCL acid and 20% gelled HCL acid were pumped in conjunction with both far field diversion and near wellbore diversion. In each case, the diverter pills consisted of 3 far field pills and 2 near-wellbore pills to aid in optimal placement of the acid. The goal of the far field pills is to improve the stimulated reservoir volume by encouraging greater complexity within the fracture network via tip screen-outs of dominant fracture channels. The goal of the near-wellbore pills is to improve cluster efficiency by ensuring that fluid is being distributed evenly throughout the target zone. Differing amounts of FF diverter were used from job-to-job in order to evaluate the effect that diverter volume has on net pressure. Regarding amounts of NWB diverter used, the volumes deployed per adjusted based on the number of perforations for each well. The results are laid out below.

Products Deployed:

Data:

Data from each of the 3 wells:

Well #1

Notes:

·         The far field (FF) pills consisted of 300 lbs of FF White

·         The near wellbore (NWB) pills consisted of 25 lbs of Div+ 917

·         The green lines indicate the net pressure trend at various intervals throughout the treatment

Observations

·         The 1st FF pill improved the net pressure trend from slightly negative to slightly positive

·         The 1st NWB pill resulted in a treating pressure increase of about 80 psi

·         The 2nd FF pill improved the net pressure trend from slightly positive to more positive

·         The impact of the 2nd NWB pill is difficult to assess due to a reduction in rate

·         The 3rd FF pill had minimal effect on net pressure trend, however positive slope was observed throughout the remainder of the treatment

Well 2

Notes:

·         The far field (FF) pills were increased to 400 lbs of FF White

·         The near wellbore (NWB) pills were increased to 35 lbs of Div+ 917

·         The green lines indicate the net pressure trend at various intervals throughout the treatment

Observations

·         The 1st FF pill improved the net pressure trend from negative to neutral

·         The 1st NWB pill resulted in a treating pressure increase of about 120 psi

·         The 2nd FF pill improved the net pressure trend from negative to neutral

·         The 2nd NWB pill resulted in a treating pressure increase of about 50 psi

·         The 3rd FF pill improved the net pressure trend from negative to neutral

Well 3

 Notes:

·         The far field (FF) pills remained at 400 lbs of FF White

·         The near wellbore (NWB) pills were decreased to 12 lbs of Div+ 917

·         The green lines indicate the net pressure trend at various intervals throughout the treatment

Observations

·         The 1st FF pill appeared to deposit in the near wellbore region, and had little effect on net pressure trend

·         The 1st NWB pill resulted in a small treating pressure increase of about 35 psi

·         The 2nd FF pill improved the net pressure trend from neutral to positive

·         The 2nd NWB pill resulted in minimal treating pressure increase

·         The 3rd FF pill improved the net pressure trend from slightly positive to positive