Unique Ultra Light-Weight Cernent Slurry Compositions for Use in Unique Well Conditions, Laboratory Evaluation, and Field Performance

Abstract

In many areas of the Middle East severe lost circulation problems encountered while drilling and cementing are commonplace. However, due to recent technological developments in ultra light weight cement compositions the feasibility of obtaining mud and cement returns in these situations has been greatly improved. Introduction In the Middle East operators commonly drill "blind" with water due to the endless ability of numerous formations to consume fluids. many attempts have been made to place a cement slurry past these intervals. place a cement slurry past these intervals. Past experience has shown that conventional Past experience has shown that conventional (water extended) light weight slurries are far too heavy to successfully use. Therefore, it is common to have several casing strings in a well where only a shoe job has been achieved. Often sulfide-containing waters corrode through these three or four strings of uncemented casing and eventually break into the production string. Extensive remedial operations are required to repair bad casing and shut-off downhole interzonal water or hydrocarbon flows. The expense involved in Performing top out jobs, remedial squeezes and setting tie-back liners has convinced several operators that it is critical to achieve a competent primary cementing job. Two new ultra light cementing processes are available today that help provide successful cementing operations even when faced with the troublesome formations and immense lost circulation problems of the Mideast Region. Both processes involve the use of inert gas to reduce slurry density. One requires preparation of a stabilized foam cement, while preparation of a stabilized foam cement, while the other utilizes an additive with encapsulated gas inside High Strength Micro Spheres. This paper outlines some of the laboratory testing Procedures used, the physical properties observed and results physical properties observed and results received from actual field applications in the Mideast. STATEMENT OF THEORY AND DEFINITIONS Conventional light weight slurries have a lower weight limit of approximately 11 pounds per gallon. This limit is achieved pounds per gallon. This limit is achieved primarily by adding extra water with primarily by adding extra water with bentonite or silicate extenders and occasionally by utilizing light weight fillers as the slurries' main ingredients. Thus the amount of cementatious material is greatly diluted which in turn affects the overall physical properties of the cement. There are several properties of the cement. There are several physical trends that are observed when physical trends that are observed when preparing light weight cementing compositions. preparing light weight cementing compositions. Many times these are overlooked when selecting a slurry design for a particular well. In general:*As the slurry weight decreases the amount of added water increases*As the slurry weight decreases the slurry yield increases*As the added water increases the thickening time increases(at the same temperature and pressure)*As the thickening time increases the 24 hour compressive strength development decreases*As the slurry weight decreases the compressive strength decreases*As the slurry weight decreases its permeability after set increases P. 379

Foamed Cement Applications in Oil Industry Based on Field Experience: A Comprehensive Review

“…The dilution of cement and the insulation effect of gas can result in a less pronounced thermal change compared to that of conventional extended cements. The thermal gradient will be more pronounced in cap and tail cements, whereas the foamed cement may show a thermal gradient similar to or lower than the normal background. , Therefore, having a cap helps in detecting foamed cement tops; without it, it may be difficult to identify foamed cement.…”

“…The thermal gradient will be more pronounced in cap and tail cements, whereas the foamed cement may show a thermal gradient similar to or lower than the normal background. 45 , 90 Therefore, having a cap helps in detecting foamed cement tops; without it, it may be difficult to identify foamed cement.…”

Evaluation and Optimization of Low-Density Cement: Laboratory Studies and Field Application

“…Examples of LDCs are waterextender cements, foam cements, and hollow-microsphere cements. Water-extender cements are limited in density to nearly 11.5 lbm/ gal (Tanner and Harms 1983). Cement fallback often occurs, and top of set cement can be 100 ft below the ground level because the formations cannot withstand the hydrostatic load exerted by water-extender cements even if full circulation is maintained to the surface and cement returns are noted (Mukhalalaty et al 1999).…”

“…The only two types of LDCs that can be used to avoid multistage-tools failure are foam cement and hollow-microsphere cement (Tanner and Harms 1983). We will focus on hollow-microspheres cements in the present study.…”