Влияние микрокремнезема на физические свойства тампонажного камня

In 2012 by request of JSC"TNK-BP Management", in the Scientific laboratory "Technological liquids for well drilling and casing" of the Perm National Research Polytechnic University (PNRPU) works on assessing the properties of the cement materials developed by three foreign and one Russian service companies were carried out. These blends were announced as the cementing materials that had been specially designed for oil and gas well casing and cementing in the areas of Western Siberia and the Far North, where the presence of permafrost (PFR) in well profiles have made their use more complicated. The received testing results of the presented cement slurry – stone indicate that the signs of failure in the samples being tested for frost resistance are first indicated after 2 to 4 cycles of freezing and thawing. The samples showed fractures, flaking or chipping off. The maximum number of the "freeze and thaw" cycles prior to decreasing of cement stone strenght in the most frost-resistant of the blends presented for testing was 5, which is not enough to be able to predict a long-term integrity of cement stone incorporated in casing and cementing of the well. To increase the quality of casing cementing within the intervals of permafrost rock formation, the employees of the PNRPU developed a new cementing blend with higher frost-resistance properties of cement stone. This special cement material is based on a highly active cementitious agent – magnesium oxide. The major advantage of this newly designed magnesia cement slurry is the higher frost resisting ability of cement stone as compared to those being tested. The reason for this is low capillary fluid content. The cement stone in such cementing material endures over 15 cycles of the "freeze" and "thaw" test. Among the positive characteristics of the cement slurry-stone which is viewed as perspective when used for casing cementing in the continuous permafrost zones are as follows: –possibility to achieve a lightweight cement slurry;–zero ice-thawing during putting the slurry into casing string annulus;–low rates on water separation and cement-water sedimentation of cement slurry;–good harden ability of cement slurry and strength development of cement stone at lower temperature;–adhesive bond formation between cement stone and ice. The achieved magnesia cement blend can be used for experimental and industrial testing during casing cementing, when the casing strings extend through the perennially frozen rock deposits.

Works related to the drilling of a deep borehole must take into account the specific conditions at its bottom. This applies especially to high temperatures, exceeding 90–100°C, and pressures of 60–80 MPa. Such difficult downhole conditions have often posed many problems when developing appropriate compositions of cement slurries used for sealing columns of casing pipes. With each passing year, drilling companies make deeper and more complicated boreholes, more and more often exceeding 3000 m, which require the use of specially developed recipes of cement slurries when sealing the casing column. In deep boreholes (with very high temperature and pressure), a serious problem is to ensure a long pumping time of the cement slurry, which should be characterized by low viscosity, little or no free water and the lowest filtration possible. Therefore, it is necessary to select appropriate retardants that are resistant to high temperatures and additives ensuring the appropriate technological parameters of the slurries and cement stone. Pressure and temperature parameters increase with the depth of the borehole. Reservoir waters (brines of different mineralization) largely affect the hardened cement slurry, therefore cement slurries intended for deep boreholes should contain in their composition additives that increase thermal resistance, delay setting, lower filtration and improve resistance to chemical corrosion caused by the action of brines reservoir. The aim of the laboratory research was to develop innovative formulas of cement slurries for sealing boreholes, both crude oil and geothermal, with increased temperatures (up to about 130°C) located in the Carpathian region. During the implementation of the topic, laboratory tests were carried out on both cement slurries and cement stones obtained from them. Due to the industry’s interest in acquiring energy from sources other than crude oil and natural gas, a broader scope of laboratory tests covered cement slurries for sealing geothermal boreholes with controlled rheological parameters, which can be used at high reservoir temperatures to seal deep boreholes. The cement slurries were prepared with tap water with the addition of potassium chloride in the amount of 3, 6 and 10% bwow (in relation to the amount of water). The following agents were successively added to the mixing water: defoaming, adjusting the setting and thickening time, plasticizing and reducing filtration. Cement slurries were made with the addition of 10% latex and a latex stabilizer in the amount of 1% bwoc (both components in relation to the weight of dry cement). The other ingredients: microcement (nanocement), microsilica, hematite and cement were mixed together and then added to the mixing water. All cement slurries were prepared on the basis of drilling cement G. When all components blended, the cement slurry was mixed for 30 minutes followed by laboratory measurements such as: density, fluidity, readings from the Fann apparatus, water retention, filtration, thickening time. From among the developed cement slurries, those with the best rheological parameters were selected, then samples of cement stones were prepared from them. Cement slurries were cured for 48 hours in an environment of high temperature and pressure (downhole conditions). The obtained cement stones were tested for: compressive strength, bending strength, porosity, adhesion of cement stone to steel pipes.

<span style="font-size: medium; font-family: Calibri;">The use of elastomer additives to solve the problems in oil well cementing has been investigated in recent years by several research groups in the petroleum industry. This study includes the laboratory examination of the effect of elastomer additives on the physical properties of heavy-weight oil well cement. In the research process, a candidate well is selected and the properties of the cement slurry used in a problematic section of the well are tested in the laboratory. Then, elastomer additives are added as an elastic agent and the improvements in the cement slurry and stone properties are studied. This article discusses the problems associated with the conventional heavy-weight oil well cement used in the candidate well and reports the detail of the improvements in cement properties obtained by adding an elastomer additive to the cement slurry formulation as an elastic agent. These properties include cement slurry rheological properties, free water, fluid loss, thickening time, cement stone elasticity properties, and compressive strength. The elastomer additive increases the yield point and plastic viscosity, but it decreases the free water and fluid loss of cement slurry. In addition, the cement stone compressive strength decreases; however, there is an optimum concentration of the elastomer additive at which the maximum compressive strength is reached. Moreover, the elasticity properties of the cement stone are improved and a lower value for the Young’s modulus and a higher value for the Poisson’s ratio are achieved. The theories supporting the results are discussed in the discussion section. The results of this study can be used to optimize the cement slurry design in any given set of conditions.</span>

Flow after cementing in oil and gas wells was first recognized as a problem in the 1960s but its full impact was not realized by the industry until recently. Cement slurry properties, such as density, rheology, fluid loss, gelation and setting time, have been suggested as contributing to flow after cementing One property of cement slurries that has not been discussed is water separation. An attempt has been made in this paper, based on laboratory tests and field results,to identify the relationship between water separation in a cement slurry and the loss of hydrostatic head of a cement column andto discover the role of designing cement slurries with little water separation to control and/or prevent flow after cementing. Introduction The term "flow after cementing" describes the events that occur when formation fluids enter the wellbore after a string of pipe such as a casing or a liner, has been cemented in place. The intrusion of formation fluids can push the drilling mud and cement slurry from the annular space surrounding the pipe. This can often be observed at the surface as pipe. This can often be observed at the surface as a flow of fluids, usually unset cement, out of the annular space. If left unchecked, the formation fluids can channel to the surface and cause a blowout. Flow after cementing is most serious when the fluids are coming from a high pressure gas sand in a deviated hole. The problem likely occurs because the cement column does not exert the hydrostatic pressure on the formation teat would be expected based on the slurry density. Various slurry properties have been considered as factors in prevention of flow after cementing. The fluid loss characteristic of the cement has received the most attention. Fluid loss can be important when cementing across permeable sands, but as one investigator pointed out, this parameter is more likely controlled by the drilling mud filter cake and mud particle invasion than by additives in the cement slurry. The loss of hydrostatic head of the cement column can result from the thixotropic property of the unset cement. Some slurries, because of this gelation characteristic, are self supporting in the annulus. These slurries may not exert expected hydrostatic pressure at the bottom of the hole and yet have no pressure at the bottom of the hole and yet have no compressive strength. Cement slurries should have a minimum safe thickening time with a very short period between the API measured thickening time and the development of compressive strength. Other slurry properties, such as uniform mixing, rheology, and properties, such as uniform mixing, rheology, and premature setting of cement high in the annulus, all premature setting of cement high in the annulus, all have a place in controlling flow after cementing. One parameter which has not received much attention is the free water content of the cement slurry. (For a description of the standard technique for measuring free water, see the "Free Water Measurement" section of this paper.) The following Mobil field experience pointed out the effects that free water content can pointed out the effects that free water content can have on the control of flow after cementing. FIELD EXPERIENCE Mobil Research and Development Corporation's Field Research Laboratory began working on the flow after cementing problem in 1976. Mobil Oil encountered the problem when setting the 13 3/8-inch casing in a number of wells in the High Island area of the Gulf of Mexico. Field personnel tried to solve the problem with fluid loss control. They reduced the problem with fluid loss control. They reduced the fluid loss from 1200 ml in the standard test to approximately 200 ml. The wells in which fluid loss control was tried had a more severe flow problem than previous wells. A laboratory study showed that the previous wells. A laboratory study showed that the fluid loss additive used had a detrimental effect on water separation. Slurries containing this additive had water separations in excess of 30 ml in the standard test. A slurry containing light weight cement, attapulgite clay and calcium chloride (when required as an accelerator) was recommended for these jobs.

Fe2O3 nanoparticles improve the physical properties of heavy-weight wellbore cements: A laboratory study

This study experimentally investigates the effect of multi-walled carbon nanotubes (MWNT’s), as a reinforcing material, on the physical properties of heavy-weight oil well cements. A candidate well is selected and the properties of the cement slurry used in a problematic section of the well are tested in the laboratory. Carbon nanotubes (CNT’s) are added as fibers to the cement slurry and the improvements in the cement slurry and stone properties are studied. This work discusses the problems associated with conventional heavy-weight oil well cement used in the candidate well and reports the detail of the improvements on cement properties obtained by adding CNT’s to cement slurry formulation. These properties include cement slurry rheological properties, free water, fluid loss, thickening time, cement stone elasticity, and compressive strength. When only 1 wt.% of CNT is added to the cement slurry, the yield point and plastic viscosity increase by eight and five times respectively, while the free water and fluid loss of cement slurry are reduced by 85% and 70% respectively. In addition, cement stone compressive strength increases by 73.8%. Moreover, the elastic properties of the cement stone are improved and higher values for the Young's modulus and Poisson's ratio are achieved; however, there is an optimum concentration of nano-additive at which the maximum yield point, plastic viscosity, compressive strength, Young's modulus, and Poisson's ratio are reached. The results of this study can be used to optimize the cement slurry design in any given set of conditions.

When constructing deep wells for oil and gas production in difficult geological conditions, special lightweight oil-well cements are used. To reduce the density and water separation of the cement slurry as well as to increase the strength, corrosion resistance of cement stone and the quality of well cementing, opal-containing rocks, fly ash, microsphere and other lightening additives are introduced into the cement composition. The influence of sedimentary rocks, such as opoka, tripoli, and diatomite containing from 43 to 81% amorphous silica on the grindability, rheological and physical-mechanical properties of lightweight oil-well Portland cement has been studied. The twelve cement compositions with different content of additives (from 30 to 45%) that meet the requirements of the standard for density, spreadability, water separation, thickening time and flexural strength were selected. The introduction of 45% diatomite or tripoli significantly reduces the duration of cement grinding, provides the cement slurry with water-cement ratio of 0.9 with better density and flexural strength, respectively, 1480 kg/m3 and 1.1–1.5 MPa.

The primary focus in designing a cement slurry for wellbore cementing is to ensure its strength and long-term integrity. To obtain high-strength cement-based materials, the influence of basalt fiber as a reinforcement was studied to create a cement slurry with high compressive and flexural strength. Deformation of the cement under loading was also investigated during the testing process. For the study, a cement plug was created using Portland cement with a water-cement ratio of 0.5. Different concentrations of basalt fiber (0.1%, 0.5%, 1%, and 2%) were added to the mix. Strength tests were carried out on the cement stone samples after 2, 7, and 14 days. The results showed that reinforcing the cement with basalt fiber significantly improved both its strength properties and plasticity. The addition of fiber led to an 11% increase in both compressive and flexural strength. Among the different fiber concentrations tested, 0.5% basalt fiber yielded the most successful outcomes, providing the highest strength characteristics for the cement stone while preserving its fluidity as a cement slurry. These findings offer valuable insights for the practical use of basalt fiber-reinforced cement slurry in constructing oil and gas wells, ensuring their durability and long-term performance.

Nanotechnology is a new method of approaching the design and production of components of very small sizes, which allows for obtaining products with unique properties and functional functions. Among a number of materials modified using nanotechnology, we can also distinguish a commonly known and used building material, cement. This monograph discusses a number of issues related to the eradication of nanotechnology for the preparation of cement slurries used to seal boreholes. In recent years, the technology of preparing cement slurry in boreholes has often involved the use of increasingly finer additives to fill free spaces in the cement matrix. Nanocomponents are perfect for this purpose, such as nano-SiO2 and nano-Al2O3, which significantly improve the parameters of the liquid and hardened cement slurry. They reduce free fluid, i.e. the so-called free water from slurry and filtration, which is particularly important in the case of cementing directional boreholes. The use of nanoadditives also causes, among others, increasing the plastic viscosity and yield point of cement slurries as well as significantly shortening the gelling and setting time of cement slurries. In the case of nano-SiO2 and nano-Al2O3 slurries, an increase (compared to conventional slurries) in the value of compressive strength can be observed, resulting from the tight packing of very small nanoparticles in the cement matrix. The microstructure of slurries with nanosilicon and aluminum oxide is compact and characterized by low porosity, as evidenced by the photographs included in the monograph, taken under a scanning microscope and by tests performed on a mercury porosimeter. The porosities of samples containing nanoadditives are much lower compared to the porosities of conventional slurries. Thanks to the use of slurries containing nanocomponents, there is a minimal risk of creating channels for the flow of formation media in the cement sheath of the borehole. The compressive strengths after 28 days of hydration are high (for samples with the addition of appropriately selected nanoadditives, they reached almost 40 MPa). Adhesions to steel pipes of cement stones containing nanoadditives are also high (often approx. 5 – 6 MPa). Moreover, the use of innovative technology in the form of carbon nanotubes in slurries also has a positive effect on the increase in mechanical strength and microstructure of cement stones. Cement stones modified with the addition of nanotubes are characterized by very high compressive strength values and high adhesion to steel pipes. They have a compact microstructure with a low content of macropores. Nanotubes can be successfully used in cement slurries in a wide temperature range (from 20°C to even up to 150°C). The possibilities of using cement slurries enriched with nanocomponents or carbon nanotubes presented in this monograph significantly expand the range of available recipes that can be used for optimal cementing of boreholes. In the coming years, slurries with nano-additives may be used in cases where it is necessary to obtain extraordinary tightness of the cement sheath in a borehole. Keywords: cement slurry, cement stone, nano-silica, nano-alumina, carbon nanotubes, borehole cementing.

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 213763, “Use of Innovative Resin-Cement Blend To Enhance Wellbore Integrity,” by Wajid Ali, Faisal A. Al-Turki, and Athman Abbas, SPE, TAQA Well Services, et al. The paper has not been peer reviewed. _ A major challenge occasionally faced during a well’s life cycle is the buildup of sustained casing pressure (SCP). Compromised cement-sheath integrity is one of the primary reasons for such a pressure buildup. Meeting this challenge requires development of an isolation material that can enhance the mechanical properties of cement. This paper presents the laboratory testing and application of a resin-cement system in a scenario where potential high-pressure influx was expected across a water-bearing formation. The resin-cement system was designed to be placed as a tail slurry to provide enhanced mechanical properties compared with a conventional slurry. Introduction The objectives of this study were to investigate the use of new systems at different densities with epoxy resin as an additive and to demonstrate value added in terms of improved mechanical properties and bonding. The resin used in this study is diglycidylether of bisphenol-F, a linear epoxy resin formed by reacting bisphenol-F with a suitable amount of epichlorohydrin and hydroxide. Amines are used as curing agents for epoxy resins. The curing mechanism is a step-growth polymerization. The curing is observed initially by an increase in viscosity and then by hardening. The final product’sproperties, in terms of compressive strength and viscosity, also are affected by the type and concentration of the amine. Aliphatic amines produce more-flexible types of epoxy resins compared with aromatic amine curing agents. Aromatic amines will produce a stronger, harder epoxy resin. Experimental Study Cement Slurry Preparation and Testing. The cement slurry was formulated and mixed with a maximum speed of 12,000 rev/min for 15 seconds and then at 4,000 rev/min for 35 seconds. To condition the cement slurry, an atmospheric consistometer was used. A viscometer was used to measure rheological properties. Thickening time tests also were conducted. Fluid-loss measurements (dynamic and static) were performed on the prepared cement slurry. Dynamic fluid loss can affect rheology and thickening time of cement slurries. Static fluid loss can result in reduction in cement slurry and allow formation fluids to enter the cement slurry. Separation of water is observed when a cement slurry is allowed to stand for a period before it sets. To determine the extent of water separation, a free water test was performed to determine the extent of water separation. The test was conducted by allowing cement slurry to stand in a 250-mL graduated cylinder for 2 hours. The cement slurry was poured into a cylindrical cell and lowered into a curing chamber. While maintaining pressures and temperatures, the cement slurry was cured up to 30 days. At the end of the curing period, the pressure and temperature were reduced to ambient conditions and the test specimens were removed from the curing chamber to be tested for mechanical properties.

One of the critical factors of cementing process in oil drilling of off-shore-project is designing the cement slurry. For this reason, the slurry properties which have been classified by American Petroleum Institute (API) should be changed so it will match with the requirement of reservoir condition. Changing the slurry properties can be done by adding the additive material into the cement slurry such as Calcium Carbonate and Silica Fume. The research objective is to study the effect of calcium carbonate and silica fume to the compressive and shear bond strength of oil well cement. Fourty five cylinder specimens with the size of (75 x 150) mm were made for compressive strength testing and fourty five cylinder specimens with the size of (25.4 x 50.8) mm were made for shear bond strength testing. Five variants of the specimen were made in this study. The variant were cement slurry with (0% Calcium Carbonate + 0 % Silica Fume) as a reference specimen; (5% Calcium Carbonate + 5 % Silica Fume); (10% Calcium Carbonate + 10 % Silica Fume); (15% Calcium Carbonate + 15 % Silica Fume); (20% Calcium Carbonate + 20 % Silica Fume). The oil well cement specimens were tested in 7, 14, and 28 days. The experimental results show that the compressive strength of oil well cement will decrease when it is added with calcium carbonate and silica fume. The shear bond strength of the oil well cement increases for the specimen with 5 % Calcium Carbonate + 5 % Silica Fume. However, the shear bond strength will decrease when content of the Calcium Carbonate + Silica Fume more than 5 %. Based on the result of this research, the optimum amount of calcium carbonate and silica fume that can be use is 5%, because with 5% of calcium carbonate and 5% of silica fume, the reducing of compressive strength is the smallest and the shear bond strength is increased compare to the others specimen with 10%, 15%, and 20% calcium carbonate and silica fume.

Rheological and mechanical properties of oil-well cement reinforced by hybrid inorganic fibers

Summary Substantial regions of hydrocarbon production in California consist of formations that are very fragile, which imposes a density limit on the cementitious system used to cement the well pipe. Also, troublesome fallback problems have been experienced for years in these areas. problems have been experienced for years in these areas. Fallback can possibly reduce production by causing formation damage. Usually, the use of foamed cement offers a low-density cementitious material that develops adequate compressive strength while avoiding fallback problems that are caused by density. After hardening, foamed cement has reduced density, and it usually provides the advantages of temperature stability and heat insulation properties. In this paper, the properties of foam cements are discussed and paper, the properties of foam cements are discussed and more than 60 cementing jobs completed with foam cement are summarized. Introduction The recent availability of foam cement as an oilwell services product has offered a new procedure to circulate cement slurry past formations having exceptionally difficult lost circulation tendencies. Certain areas of California hydrocarbon production are overlain by several highly permeable, unconsolidated sand and gravel bed permeable, unconsolidated sand and gravel bed formations that have very low reservoir pressure and low fracturing gradients. Also prevalent are naturally fractured shaly sands and shale formations that consistently pose lost circulation problems during the drilling and cementing operations on wells located in Kern County, CA. If circulation is maintained to the surface during cementing and cement returns are achieved, fallback often occurs such that the top of set cement is found many feet (often hundreds) below ground level. Therefore these formations are incapable of supporting the hydrostatic load exerted by conventional-density cement slurries throughout the cement hardening period. In the past, numerous attempts have been made to cement these types of fragile formations. The use of ordinary lightweight cements extended with bentonite, fly ash silicates, perlite, diatomaceous earth oil emulsions, or gilsonite, as well as the use of thixotropic cement slurries, has been attempted, but when applied to exceptionally pressure-sensitive lost circulation zones these slurries have provided limited success. To a large degree, the conventional slurries have not been successful because their densities can be lowered only to approximately 11 to 12 Ibm/gal [4.9 to 5.4 kg/m 3] (1.32 to 1.44 specific gravity) before their useful strength and permeability properties are compromised. Multistage techniques that properties are compromised. Multistage techniques that use conventional lightweight cement slurries also have afforded limited success. In addition, the total cost of this type of approach can be prohibitive. Two types of cement slurries currently are available that can achieve densities much lower than 11 Ibm/gal [4.9 kg/m 31. The first type incorporates pressure-resistant hollow microspheres into cement slurries. High-strength microsphere slurries continue to be used successfully in oilwell cementing. The relatively high bridging ability of the hollow beads enhances their effectiveness in controlling lost circulation. The second available type of ultralow-density cement slurry results from the preparation of a stabilized, gas-containing foam cement slurry. preparation of a stabilized, gas-containing foam cement slurry. Foam cement is successful because of its ability to keep cement slurry density below the hydrostatic breakdown gradient of the sensitive formations. A general comparison of typical physical properties of conventional and foam cements is given in Table 1. It was reported earlier 12 that foam cement could be used to seal underground storage caverns, insulate wellbores, and perform remedial squeeze jobs. Subsequent reports substantiated the basic properties of foam cement. Relatively little information properties of foam cement. Relatively little information has been published that describes the use of foam cement in primary cementing applications. This paper will focus on the use of foam cement as a primary cement in severe lost circulation zones in California. Properties of Foam Cement Properties of Foam Cement A true foam cement is created when a gas is chemically and physically stabilized as microscopic cells within an ordinary cement slurry. Two uncommon factors are needed to prepare stable foam cement. First, the cement slurry should contain a high calcium ion and high-ph-tolerant foaming surfactant and foam stabilizer. Second, the slurry should be conveyed through an effective mechanical foam-generating device that imparts sufficient energy and mixing action with pressurized gas to prepare uniform gas bubbles of the correct size. Foam cement so prepared is essentially stable, unlike nitrified cement or drilling fluid; the gas does not coalesce and separate from the slurry if the slurry remains under the pressure conditions for which it was designed. Nitrogen usually is the first choice of gas since current nitrogen servicing equipment is more than capable of providing sufficient quantities of gas at suitable rates for cementing purposes. Fig. 1 illustrates the quantity of nitrogen per barrel of cement slurry needed to prepare low-density foam cements. JPT P. 1049

The influence of superplasticizer and silica fume on cement hydration, structure formation, phase composition, and cement stone properties is investigated. It was found that using a polycarboxylate superplasticizer reduces the normal consistency of the cement paste and increases the cement stone strength at 28 days by 22%. Replacing cement with silica fume in the absence of a superplasticizer does not increase the cement stone strength, but it reduces the open capillary porosity of the cement stone by 7%. The combined use of silica fume and superplasticizer increases the cement stone strength by 27% and reduces open capillary pores volume by 17% compared to the control sample without admixtures. According to the X-ray phase analysis results, it was established that the use of polycarboxylate superplasticizer leads to a slowdown in the hydration processes of clinker minerals at 1 day. The use of silica fume accelerates the cement hydration in the early hardening stages and compensates for the plasticizing admixture slowing effect. At 28 days, in the cement stone with silica fume, a decrease in the portlandite content by 39% is observed. The combined use of superplasticizer and silica fume leads to the formation of a cement stone structure with increased content of amorphized low-basic hydrated calcium silicates by 22%, which significantly densifies and strengthens the cement stone structure.KeywordsCement stoneSilica fumeSuperplasticizerNormal consistencyCompressive strengthPorosityPhase compositionPozzolanic reaction

Unlike oil well, gas well cement formulation requires special additives to take care of the microannuli that may arise as a result normal water cement ratio. The normal water cement mixing ratio usually yield low volume of cement slurry with attendant problem, chief of which is shrinkages. Hence, calcium oxide is used to expand the cement to mitigate against shrinkages and subsequently increase the slurry’s yield. The expanded cement ensures the integrity of wellbores and prevents the migration of fluids into the wellbore.Traditional oil and gas well cements are composed primarily of Portland cement, water, and admixtures. However, concerns over environmental sustainability and resource depletion have driven the exploration of alternative cement additives, such as pozzolanic materials.Pozzolanic materials, such as silica fume, rice husk ash, and palm oil fly ash, have emerged as promising alternative additives in formulating cement slurries due to their sustainability benefits and potentials to enhance cement properties.The fracture pressure of the weakest formation is usually considered when formulating cement slurry. In formulating the cement slurry under investigation, a fracture pressure of slurry density of 15.4 ppg equivalent was used.The normal mixing ratio of 0.44 as per API standard would give 15.8ppg. With a specific gravity of 3.25, calcium oxide is a density increasing material which allowed for the use of considerably lower amount of water, silica fume is a density reducing material, hence the use of higher amount of water. The incorporation of calcium oxide (25 % BWOC) and silica fume (15 % BWOC) lowers the slurry density to 15.4ppg. The results obtained at 100 Bc consistencies showed a gradual decrease in thickening time with increase in temperature in both the expanded and nonexpanded cements. The porosity of the expanded was determine using fresh and saline water and was found to be lower than 0.05 % which shows that the silica fume acted on the micro spaces in the cement.