Schlumberger

Case Study: SILDRIL Used To Successfully Drill Shallow Gas Section

Gulf of Thailand

Challenge:

The operator had previously encountered problems while trying to drill and case the surface hole. They wanted to be able to seal off the shallow gas sand in the upper section, while at the same time drilling a gauge hole that would be successfully cased and cemented.

The Gas influx from this sand had plagued drilling operations to TD behind subsequent casing strings.

There was also a penalty to pay for short delivery of the daily gas production if this was not successful as well as the likelihood of relocating the entire production platform.

Solution:

Although M-I did not hold the contract with this operator, we offered to supply a silicate system to solve this unique and costly problem. This opportunity arose from our local reputation and M-I’s regional plus global experience with the SILDRIL System. A mud program was written using 8% SILDRIL by volume and 4% KCl by weight. Using M-I’s SILDRIL system the surface hole sections were drilled under-budget and ahead of time.

Result:

To provide maximum inhibition throughout the gas sand, the 12¼” hole sections were batched drilled with SILDRIL water based mud. Seven surface hole sections in total were drilled and cased with no problems. The operator was extremely happy with the results as the gas sand was drilled, cased and cemented with no further problems. A caliper log was run on the first well and indicated the hole size to be 12.54”.

All the wells were drilled in “slide” mode, rotary was used at the end of the section while circulating the hole clean. Cuttings transport was good, even when sliding. The cuttings quality throughout was excellent. The hole was lightly back-reamed while pulling out for running of casing.

Well Information
Location Gulf of Thailand
Spud / Completion 10th August 2002 / 19th August 2002
Total Depth 410-415m
Intervals Drilled Seven 12¼” Hole Sections (batch drilled)
Maximum Density 1.10SG
Total days on Wells 10 days

Benefits of the SILDRIL System

  • Resulted in stable well bores
  • Achieved Objectives
  • Saved time and money

The Details

The silicate was sent to the rig in 200 liter drums and all the mud was mixed at the rig site. 140m3 of mud was mixed in the pits initially. The cement inside the previous casing was drilled with seawater to avoid contamination of the SILDRIL system. The mud weight for all the wells was 1.10SG.

The system was run with 8% SILDRIL, 4% KCl, 1.0 ppb fluid loss agent (PAC) and 1.5 ppb viscosifier (xanthan gum).


Download: SILDRIL Used To Successfully Drill Shallow Gas Section (0.50 MB PDF)

Contact Us
“By successfully drilling and cementing the seven 9⅝” casings sections across the problematic shallow gas sand, you gentlemen have saved PTTEP and Partners some 10 million US$. If PTTEP had not been able to seal this zone, we would have had to relocate the platform and incur a penalty for the short delivery of the daily gas production quota until such time that new production potential was established. In the past six months, there have been several attempts to solve this problem with results nowhere near the success we have now experienced.”
Pornpoch Tiraputra
Drilling Manager
PTTEP