Cementing Technology for Low Fracture Gradient and Controlling Loss Circulation

Abstract

TX 75083-3836, U.S.A., fax 1.972.952.9435. AbstractThe main objectives in well construction are to maximize reservoir deliverability, reduce remedial jobs, and minimize nonproductive time (NPT) during drilling and cementing. One of the key factors to help maximize reservoir deliverability is the ability to reach the target reservoir depth with a minimum number of casing points and maximum production tubing size for the completion. Losses during drilling and cementing should be controlled to reduce unplanned casing points and minimize the NPT.These challenges are severe in depleted and low-fracturegradient formations. Engineered solutions to control loss circulation and to place cement slurry in these environments are presented and discussed. Controlling loss of circulation during well construction is more than just selecting the proper type of lost circulation material (LCM). The engineered solution discussed in this paper correlates the formation and LCM properties for effective control of losses. In situations where LCM alone may not reduce the losses, the use of chemical sealants such as polymers and special cement systems are discussed. The special cement systems can be designed to meet the specific needs such as acid solubility for easy removal, thixotropy, and filtrate loss.Cement slurry for primary cementing across low-fracturegradient and depleted formations should be designed to meet the density requirement so that it can be placed in the annulus and losses can be minimized. Ultra-low-density cement slurries, as low as 5.4 lbm/gal, are presented and discussed. Case histories are also presented to illustrate field implementation procedures, and the optimization of cement slurry designs to meet well requirements is discussed as well.The results presented in this paper can be applied in well construction to control loss circulation and cementing across depleted and low-fracture-gradient formations, which ultimately should help reduce NPT and maximize well production.

Nanosilica-Based Loss Circulation Composition to Cure Moderate to Severe Losses

“…These low-density or foamed cement systems have been designed with a special acid-soluble cement along with some polymers. The cement slurries have been designed to manage low-fracture gradient formations by reducing loss circulation challenges [28]. Crosslinked cement systems comprising a stoichiometric mixture of magnesium and calcium oxides, carbonates, and sulfates have been described.…”

A Polymer Plugging Gel for the Fractured Strata and Its Application

“…The traditional and most common plugging method is bridge plugging, which is when the plugging materials are used as padding and bridging to form a plugged zone with a suitable strength [ 10 , 11 , 12 , 13 , 14 ]. However, the fracture size of the fractured strata changes a lot, which can cause the bridge materials to find it difficult to enter the fracture or to find it hard to form the bridge plugged zone [ 15 , 16 , 17 ]. This kind of well leakage accident is a really troublesome problem in the downhole, which can result in a large loss in terms of both the economic cost and drilling time, and can even do harm to drilling workers.…”