Curtis G. Blount

HCl/HF Acid-Resistant Cement Blend: Model Study and Field Application

Analysis of Prudhoe Bay field stimulation data suggests that HF-acid treatments are harmful to wellbore cement. Laboratory tests confirmed the suspected solubility of conventional oilfield cements in hot-acid solutions. Test results indicate that a 2-in. cement cube is up to 96% soluble in a dynamic solution of 12% HCl/l3% HF (mud) acid at 190{degrees}F. A wellbore simulator was developed to correlate cube solubilities to downhole conditions. This paper documents equipment and testing procedures used to confirm acid solubility of cement-squeezed perforations in a typical wellbore. It also documents additive screening that led to the development of an acid-resistant cement (ARC) blend that uses liquid latex. This blend improved acid resistance by more that 700% over conventional formulations under simulated field conditions and configuration. The latex cement blend was also demonstrated to be compatible with coiled-tubing-unit cement-squeeze applications.

Dynamically Overbalanced Coiled Tubing Drilling on the North Slope of Alaska

Coiled Tubing Drilling (CTD) continues to play a dominant role in through-tubing sidetracking of wells on the North Slope of Alaska. Recently several CTD candidates were targeted in an over-pressured reservoir. Three wells were successfully CT sidetracked as a pilot project in this over-pressured reservoir. The ultra-slimhole directional drilling system -2.75 nominal openhole diameter- developed a Prudhoe Bay was used in combination with an unconventional approach to maintain overbalanced conditions when sidetracking these weils. Hydraulic modeling showed that with a kill weight drilling fluid, the calculated Equivalent Circulating Density (ECD) at the sand face could approach the regional fracture gradient. In addition, kill weight mud in the formulation required for CTD operations would be a significant expense. To address these concerns, the wells were CT sidetracked using a less expensive under-balanced drilling fluid system. Although the drilling fluid hydrostatic pressure was less than reservoir pressure, over-balanced drilling conditions were dynamically maintained by the high ECD while circulating, and controlled by increasing the surface pressure using a choke when circulating at less than drilling rates.

Annular packer fluids for paraffin control: model study and successful field application

This paper covers the evolution full-scale model study, and field application of gelled packer fluids for paraffin control in naturally flowing wells. Field application of these insulating packer fluids has resulted in significant increases in the flowing tubing temperature in the seven wells treated to date. The temperature increases from gelled-packer-fluid application along have eliminated paraffin problems previously controlled with repeated hot-oil treatments. Before this application, chemical inhibition attempts were unsuccessful. The gelled fluid currently used is based on a phosphate ester and sodium aluminate reaction that produces an aluminum phosphate ester association polymer. The gellant is commonly used in oil-based fracturing fluids.