Abstract
Cement Packer is a cost-effective alternative to workover for monetizing hydrocarbon reservoirs above the well top packer. While conventional cement packer utilizes coil tubing for cement placement, an innovative and more cost-effective approach was successfully implemented with only slickline and pumping unit, without utilizing coil tubing. This reduced the overall cost of the well intervention by 60%, significantly reduced operational safety risks and is exceptionally suitable in the current challenging environment.
Similar to conventional cement packer, the operation begins with setting a plug inside the tubing below the targeted perforation depth and punching the tubing to create tubing-casing communication. The tubing was then flushed with surfactant and weak acid to remove any potential contaminants. The cement was then bullheaded from the surface through the tubing and into the casing while being chased by two foam wiper balls. The foam wiper balls were subsequently pushed with inhibited sea water mixed with cement retarder to prevent any leftover cement from hardening in the tubing. The hardened cement column in the production casing then acts as a barrier to satisfy operating guideline for two pressure barriers in a well.
Two cement packer jobs were performed during this campaign; one via conventional method with coil tubing unit (CTU) and a fit-for-purpose version without the CTU. Pressure test from the tubing and casing after the cement hardened indicated that the cement has effectively isolated both tubulars. Subsequent Cement Bond Log and Ultrasonic Imaging Tool demonstrated thick column of good cement thus confirming the cement integrity of the non-CTU method. It was able to achieve similar pressure isolation as the conventional CTU method at 60% lower cost which allowed for significant cost saving. It also reduced the operation time by 50% since the cement was pumped at a higher rate through the well tubing. The turbulent flow regime via high rate pumping also resulted in thicker column of good cement (200m vs 120m) compared to conventional method. The only drawback encountered was the unexpected obstruction caused by leftover cement behind the foam ball. However, this can be removed through milling or fine-tuning the retarded sea water recipe. Post perforation, there was a sharp increase in the tubing pressure while the casing pressure remained low, further confirming the success of this method. This innovative method will be the standard method for any future cement packer operations while the conventional method with coil tubing will only be applied in complex situations.
This new Cement Packer technique has introduced substantial cost saving compared to the conventional cement packer method. It will enable monetization of more minor reservoirs. The method is exceptionally relevant to a mature field especially in the current challenging business environment.
