Paper: SUCCESSFUL TOP OF CEMENT ACHIEVED IN TROUBLE WELLS WITH A CONFORMANCE PRODUCT

When dealing with cementing operations with problematic formation issues, achieving satisfactory top of cement (TOC) is essential. A central Texas operator encountered zonal isolation challenges that resulted in inadequate TOCs. One of those challenges was achieving a density both above the pore pressure and below the fracture gradient. In some wells, this density window was as narrow as 0.02 to 0.04 psi/ft. Karsts and tectonic-fractured formations exist in this field, which often result in uncovered zones and TOCs at unacceptable levels. Formations such as these, with heavy erosion and cave-related brecciation, can have huge voids at volumes that are nearly impossible to measure. To meet regulatory requirements and achieve successful zonal isolation, competent cement sheaths are necessary. Initially, expensive cement-squeeze applications evolved as the zonal isolation effort was initiated in these trouble wells. However, it was decided to use a conformance product to allow the cement column to exist at a high enough level to be deemed a successful solution without the aid of the squeeze application. This
paper presents a case history of several central Texas wells in which satisfactory TOC was difficult to achieve. The challenge was to get cement high enough to meet regulatory requirements, without having to perform a squeeze job. The wells discussed exist in an environment with washed out formations occurring in a narrow window of design density. The design criteria involved overcoming these washed out regions that consume cement volume. The service company provided a solution of using a conformance product to achieve adequate TOC without the aid of a squeeze application. This paper compares several wells before and after using this water super-absorbent polymer procedure, demonstrating an improved percentage of adequate TOCs and significant cost savings to the operator.