Design of cement pulsation treatment in gas wells - Model and field validation

Document Type

Conference Proceeding

Publication Date

1-1-2002

Abstract

Top cement pulsation (TCP) is an auxiliary cementing technology for enhancing zonal isolation by applying low-frequency hydraulic pressure pulses to the wellhead immediately after placing cement in the annulus. A properly designed TCP keeps the well overbalanced by delaying the process of cement slurry thickening in the well annulus without pressure pulsation impacting the well's bottom. In the result, the slurry remains longer in liquid state, hydrostatic pressure is sustained, thickening time is delayed, and transition time is shortened. All these effects combined would improve cement quality and eliminate gas flow after cementing. The paper shows how to design TCP for a given well program and slurry properties. Using hydraulic analogy between low-frequency reciprocation of Bingham fluid and the plug flow, a mathematical model has been derived to describe the top pressure pulse attenuation with depth. The model also includes well compressibility formulas to calculate downhole transmission of the top displacement amplitude. The mathematical mode constitutes a basis for TCP treatment design and prediction. Presented in the paper is experimental verification of the design model using full-scale pulsation of a tixotropic slurry at the LSU Well facility and field data from TCP treatments in conventional and “instrumented” test wells (equipped with downhole pressure gauges). For the conventional well, the design model would calculate depth of the TCP treatment resulting in a good match between calculated and recorded values of displacement amplitude at the cement top. For the instrumented well a direct match was obtained between the measured and computed pressures at depth.

Publication Source (Journal or Book title)

Canadian International Petroleum Conference 2002, CIPC 2002

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