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Cementing Problems in Challenging Shale Gas/Tight Gas Applications in SW China

BACKGROUND

Shale gas/tight gas wells in the Sichuan Basin of Southwest China which were drilled with OBM consistently encountered significant problems following casing cementing operations. These problems included annular pressure buildup, sustained casing pressure (SCP), micro-annulus development, cement sheath failure as well as collapsed casing and mechanical well damage.

CHALLENGES

  • OBM environment
  • Significant pre-cementing background gas
  • Narrow casing/wellbore and casing/casing annulus
  • Post cementing micro annulus formation, tensile cracking and annular pressure buildup

SOLUTIONS

"Multi-FIT" customized cementing system containing FlexPlus elastomeric additive and featuring:

  • Inert components which create minimal impact to cement slurry properties
  • Improved stability and reduction of free water within the cement slurry
  • Improvement to cement flexibility and tensile strength
  • Documented improvement to cement bonding and gas migration
  • Proven reduction to Elastic Modulus allowing hardened cement to absorb stresses with reduced cracking

RESULTS

Zero annulus pressure reported following cementing operation where FlexPlus additive was used.

Elastoplastic Additive—FlexPlus Application in Southwest China Shale Gas Ops.