Improving the Performance of Drilling Fluids in the GOS of Egypt; saving two Casing Strings and completing a stable hole

A Case History
A challenging well in the Gulf of Suez of Egypt where the offset wells indicated numerous problems experienced throughout all the wells sections. The Well was drilled where both the 18 5/8” CSG & 7” Liner were saved and the wire-line logging ensured the stability of bore hole against the hydrostatic for more than 3,000psi differential pressure. DFT accepted the challenge and strived to be committed to High Quality Services. 

The Situation:
Our customer planned to have a drilling campaign of development and exploratory wells; the design of the first well was based on the following criteria:

  1. Complete loss of circulation is expected at the surface hole of Post Zeit formation that compel us setting of 18 5/8” casing in order to seal off that unconsolidated sands.
  2. Salt Water flow that compel us running 9 5/8” casing at top of Belayim Clastic formation in order to seal off that flow prior getting through the reservoir section.
  3. Unstable shale section within Belayim formation requires full inhibition.
  4. Reservoir sections of Belayim & Kareem formations require low mud density to avoid down-hole losses that cause damaging of the reservoir.

The Solution:
DFT has studied all the offset wells, carefully defined all the experienced problems, and came up with the proper mitigations. The mud systems needed some sort of modifications, the losses strategy needs to be set and finally, ideal packing technique must be formulated for the reservoir sections. Combining the reservoir section together with the Evaporites interval to save one casing string is a plus that we should work for it.

The Results:
DFT successfully drilled the entire well achieving the following results:

  1. 18 5/8” casing was saved since no complete loss of circulation was experienced due to excellent fluid properties designed by DFT technical engineering staff. The drilling process of 16” hole was advanced from 30” C.P shoe until top of South Gharib formation.
  2. 7” Liner was saved since the drilling process of 12 ¼” hole section was advanced from 13 3/8” casing shoe till the total depth of the well. Extensive lab formulations with proper study for offset data enabled DFT to decide to drill with 11.7 ppg mud density prior getting through the high-pressure interval was a correct choice.
  3. Tripping performance indicated very stable hole where no drags were encountered while tripping in and/or out.
  4. The inhibition degree of the mud system indicated excellent compatibility for the drilled shale sections. No caved or swelled shale were experienced while the drilling process.
  5. No down-hole losses were reported at the reservoir section. Losses strategy and bridging material technique that set by DFT was the first defense line against the losses issue.
  6. MDT results indicated the protection of reservoir section against the hydrostatic pressure that helped to great extent protecting the reservoir from being damaged. MDT readings indicated differential pressure of more than 3,000psi. Some points indicated more than 4,000psi differential pressure.
  7. Early production testing results showed higher rate than surrounding wells in same field prooving the excellent none damaging characteristics for the formulated system in reservoir section.

By: Hassanein Youssef
Drilling Fluids Technology Director
PICO Energy – Petroleum Integrated Services


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