3M™ Glass Bubbles HGS Series Improve Lightweight Cement Slurry Performance

   The key requirement to slurry used for casing cementing is to ensure casing annulus tightness and elimination of any annular flow. Hence cement slurry and cement stone shall meet the required rheological and structural/mechanical specifications subject to hydrogeological conditions of well constructions.

   Usually well cementing is a real challenge demanding for specific technological solutions. In some fields well construction is aggravated with permafrost rock, highly permeable formations and low porous pressure reservoirs. In the above conditions the most effective technology enabling abrupt reduction of casing cementing costs is the application of light-weight cement slurry of a designed gravity. In the up-to-date critical wells the application of the super-light cementing systems may improve well performance and cement quality, and reduce cement failure in casing. In this case the cement slurry gravity shall be equal 1.4 g/cu. cm maximum that is not typically provided in full with the existing light-weight cements and filling agents.

   Typical light-weight cements use water to reduce gravity. They also contain materials to absorb water and to maintain homogeneity of cement and cement slurry. Despite their low cost these “typical” cements have several critical disadvantages: they are essentially weak and hardly ensure durable well cementing at high loads. On the other hand these cements have the minimum gravity limit equal to 1.38 g/cu. cm.

   The so-called coenospheres or aluminosilicate microspheres are rather often used to reduce gravity to 1.14 g/cu. cm. They are produced of power plant ashes with the help of a floatation technology; however their application is limited with ultimate compression strength. A typical upper limit of ultimate strength of ceramic spheres, as a rule, is within the range from 140 to 210 atmospheres, hence limiting their application for a number of tasks.

   To prevent absorption of slurry in low-pressure formations another technology is often used: injecting nitrogen in order to foam cement. However these foam cements also have a few shortcomings such as high permeability and low strength, hence resulting in cementing failure and growth of completion costs. The application of foam cement is open to many hazards with the following restrictions: higher hydraulic friction in the well (that may result in fluid loss), unstable parameters in the course of application, troubles in cementing control from the surface, insufficient quality control and problems related to acoustic and ultrasonic cement bond logging.

   One of the most effective methods of reduction of cement slurry gravity is currently the application of the glass bubbles of low gravity and size, and, on the other hand, of higher ultimate compression strength. These parameters enable their effective use in cement slurries. Though glass bubbles have already been used in the industry for a certain period of time, the latest technological achievements made them super-light, providing at the same time perfect resistance to crushing from 140 atmospheres to 1,240 atmospheres.

   The worldwide practical experience demonstrated that super-light cement slurries with 3M Glass Bubbles HGS series have higher compression strength at lower gravity and higher durability