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Home / Issue Archive / 2009 / November #11 / 3M™ Glass Bubbles HGS Series Improve Lightweight Cement Slurry Performance

№ 11 (November 2009)

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

   Nowadays many oil and gas producers and service companies face the important task of improving the quality of casing cementing in well completions as it directly affects the reliability of operation.

By Pavel Lazarev, senior technical service engineer, 3M

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   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 to compare with typical light cement slurries.
The 3M Company developed chemically resistant sodium-borosilicate 3M Glass Bubbles. This composition makes them unyielding and insoluble in water.

   Besides, these glass bubbles are a specially designed high-tech product rather than a by-product of coal combustion. The production of 3M Glass Bubbles at Tilloy-lez-Cambrai Plant in France is regularly controlled. These checks help maintain the product’s original features and its high quality (Fig. 1).
The international and Russian practice shows that the use of light-weight cement slurry with 3M Glass Bubbles reduces spending of time and materials for well casing, and enables cement flow to the designed level with isolation of beds. The cement stone’s increased durability and crack resistance prevents the need for repeated insulation during casing perforation, and sufficiently strong cement bond ensures annulus tightness.

   The perfect spherical form of 3M Glass Bubbles provides for a number of useful properties including enhanced flow characteristics and lower blends viscosity that simplifies slurry pumping (Fig. 2). 3M Glass Bubbles HGS series are compatible with major polymers and compounds with microspheres have stable viscosity and long-life performance.

   3M Glass Bubbles were specifically designed by 3M to have a high strength-to-gravity ratio. This is the property that ensures microspheres’ high resistance to heavy loads in the well. The glass bubbles have various gravity and pressure resistance, hence adequate material may be selected for any well (Fig. 3).
The 3M Glass Bubbles HGS series’ specific gravity is 0.32-0.6 g/cu. cm enabling them to stand 140-1,240 atmospheres well pressure (Fig. 4). Besides, the additional advantage of this new HGS technology with cement slurries lies in the fact that application of this material critically simplifies hydraulic calculations due to stable gravity of prepared slurry.

   Multiple practical applications revealed that cement slurries prepared with 3M Glass Bubbles do permit to reduce costs and to improve cementing job quality to compare with other methods of gravity reduction. 3M Glass Bubbles make it possible to prepare cements with gravity as low as 1.1 g/cu. cm. Unlike low gravity cements prepared with water dilution or under other technologies, the cements prepared with the help of 3M Glass Bubbles form fast and have high strength at reduced waiting on cement – WOC.

   Low gravity cement slurries with 3M Glass Bubbles prevent the need for a multi-stage cementing job that is often required in sufficiently deep wells penetrating formations that cannot stand hydrodynamic pressure. Hence these low gravity cement slurries can enable a deep-well one-stage cementing with reduced time consumption, formation damage and, finally, total cementing costs.
Thus, low gravity cement slurries based on application of 3M Glass Bubbles HGS series is the effective and saving alternative to conventional cementing jobs in wells constructed in critical conditions of high fluid losses and large depths.

Application of this technology provides for the following technical and economical advantages:

– Higher quality of cementing.
– Lower of waiting on cement resulting in well construction time saving.
– Predictable gravity range.
– Final slurry is uncompressible.
– Simple application and use.
– Predictable actual ultimate compression strength (deep hole pressure).
– High compression strength at 12 and 24 hours exposure.
– High temperature and chemical resistance.
– Potential one-stage cementing resulting in lower cementing time to compare with a multi-stage cementing.
– Lower formation potential damage.
– Lower risk of circulation loss.
– Prevention of costs related to well problems.
– Higher cement output per a sack.

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