Cake permeability and rate of dehydration of a slurry as a function of fluid loss additive concentration (after Hook and Ernst, 1969). Cake permeability and rate of dehydration of a slurry as a function of the concentration of fluid loss additives (after Hook and Ernst, 1969).
Introduction
It would be of great interest to further investigate the bonding ability of PAC-R polymer as an additive in grade G cement for cementing oil and gas wells. Thus, this work tries to find the trend of physicochemical characteristics related to the bonding ability of PAC-R polymer in oil field cement.
Research Problem
Hypotheses
Research Questions
Objectives of the project
To evaluate the bond efficiency of PAC-R modified cement by characterizing the compressive strength and Young's modulus of the cement system.
Justification of Research
Summary
Dimensional and depth data
Essentially, the size of the open hole is determined by the size of the drill bit. However, the attenuation of the wellbore fluid limits the application of such ultrasound technology (Nelson and Guillot, 2006).
Wellbore environment, including pressure regime and drilling fluid
As noted by Sauer (1985), cement design is influenced by the physical and chemical properties of the mud. The predicted downhole parameters of the drilling fluid should be taken into account, as these data may differ significantly from those observed at the surface.
Temperature
This approach recalculates the pseudo well length (well equivalent) and uses a special equation (Kutasov-Targhi equation) to obtain the BHCT. BHST is the undisturbed bottomhole temperature.
Secondary Cementing
The law of filter cake formation for a suspension was coined by these authors (such as a cement slurry). Thus, the "law of filter cake formation" can be written as follows: q= flow rate of filtrate per unit area of surface dS/dt = rate of growth of the filter cake thickness. Relationship between slurry property, perforation geometry and height of filter cake node inner casing (after Binkley, Dumbauld and Collins, 1958).
Experimental studies were conducted by Hook and Ernst (1969) to determine the effects of formation permeability, differential pressure, and fluid loss control additives on the rate of filter cake build-up. In addition, Table 13.1 shows that filter cake permeability is indirectly related to the rate of filter cake growth. First, it was determined that the permeability of the resulting filter cake is not affected by changing the squeeze pressure from 500 to 1,000 psi (3.5 to 6.9 MPa).
Effect of differential pressure on filter cake permeability and filtration rate (experimental) (after Hook and Ernst, l969). The influence of filtration permeability on the rate of development of cement filter is shown in table 3. Effect of formation permeability on the rate of growth of filter filter (after Hook and Ernst, 1969).
Polyanionic cellulose polymer (PAC-R)
The amount of C-S-H, the primary hydrated product and gel phase in Portland systems that determines the durability and strength of concrete, is likely to be related to the amount of PAC that can minimize cement hydration products reducing potential setting time.
Compressive Strength of cement
The compressive strength of cement concrete depends on the type of raw materials, including admixtures, mixing ratios, concrete structure, drying process and duration, and environmental factors (Herianto and Fathaddin 2005). The compressive strength of the cement slurry has been improved compared to the current one. The experiment of this study showed that the compressive strength of cement slurries for certain drilling operations varies with the percentage of additives included in their design and formulation.
In this study, the effect of different additives on the compressive strength of cement was investigated and the findings of their sensitivity are clearly shown in Figures 7 and 8. 7 and 8, both filler and antifoaming agent had different effects on the compressive strength. of the investigated cement in different proportions and at different times. For example, the compressive strength of cement remains relatively constant as the filler content increases from 5% to 10%.
Above this amount, the compressive strength continues to decrease gradually and in a proportion of approx.
Materials and equipment
The spectrometer is equipped with a 7800–350𝑐𝑚−1 optimized mid-infrared KBr beam splitter and 11000–375𝑐𝑚−1 XT KBr extended-range mid-infrared optics.
Sample preparation
The cell cap threads were lubricated with high-temperature thread lubricant to prevent stickiness of the cement slurry to the cell walls. The Air to Cylinder and Pressure Relief valves are closed and the pump is turned on. After opening the “Fill cell” valve, water flows into the test cell and the displaced air is pressed out through the released air.
The temperature was set at 80℃ and the cement slurries were 1 day and 3 days.
Tensile strength measurements
Equation (2), modified by (Q.Z. Wang et al., 2004b), which takes into account the effects of loading angle, was used to obtain more accurate findings.
Microstructure analysis
If other bands are noted, they may be due to vapor, contamination of the ATR crystal, or salt plate if previously used. In this case, it is necessary to clean the surface with solvent if necessary and observe again. There are often fumes present, especially if many people clean the ATR crystal with ethanol, acetone or isopropanol.
Most samples will be analyzed using the ATR accessory as this is useful for both liquid and solid samples. Cracked samples were placed in the center of the diamond crystal at the center of the ATR plate. The IR beam has a diameter of only 0.1 mm and is aimed at the center of the diamond.
FTIR analysis is conducted to compare with standard class G cement while investigating the microstructure of a new PAC-R modified cement before and after exposure to brine and hydrocarbon at different temperatures.
Research Flow Chart
Compressive Strength Analysis
The axial stresses were calculated by the ratio between the axial loads and the cross-sectional area of the cement blocks during the uniaxial test, which is also defined as the compressive strength. The results of the uniaxial test are shown in Table 6, where. specimens with 10% and 20% PAC-R copolymer concentrations had significantly lower axial loads and axial stresses compared to the control specimens, a similar tendency observed in the studies of Sun et al. 2015), the ethylene-vinyl acetate (EVA) copolymer additive showed a gradual decrease in compressive strength for. Similar results were obtained with styrene butadiene latex (SBL) and double-coated polyacrylamide (DPAM) (Yang et al., 2015; Richhariya et al., 2020).
The reduction in the compressive strength is attributed to the existence of organic constituents within the matrix (Lanka et al., 2021). This can be attributed to the ability of the polymer to fill microcracks and voids in the cement matrix, resulting in a more homogeneous and dense matrix that can resist. Moreover, increasing the curing time from 1 day to 3 days resulted in a significant increase in the axial load and axial stress of the cement blocks, regardless of the PAC-R.
The compressive strength of cement increases with increasing drying time, as the hydration reaction between cement particles and water continues to form more cement products and results in denser and stronger cement matrix (Raheem, 2013).
Flexibility
Similar observations were reported by Thiercelin et al. 2018) who studied the ductility of grade G cement by examining the drop in modulus of elasticity with the addition of latex and an increase in setting time. Their research showed that the value of elastic modulus with added latex at curing conditions of 3 days, 80◦𝐶 and 3000 psi was 4.07 GPa. The lower values obtained from the test results of the PAC-R cement in the investigation can be attributed to the different setting conditions and the absence of pressure during the shorter setting time compared to the rest of the cement system.
This difference in hardening conditions may explain the lower values obtained when compared with latex cement. However, in oil and gas well cementing, very low Young's modulus values may indicate insufficient cement strength and stiffness, potentially leading to cement failure and reduced zonal isolation.
FTIR analysis
In the case of PAC-R additive with cement, the peak at 2950 𝑐𝑚−1 may be influenced by the presence of the organic polymer. The presence of the PAC-R additive in the cement may contribute to the intensity of the peak at 2950 𝑐𝑚−1 in the FTIR spectrum. This peak is usually observed when the sample is exposed to air, as CO2 in the atmosphere can react with the free calcium hydroxide (Ca(OH)2) in the cement to form calcium carbonate (CaCO3) through carbonation.
Therefore, the peak at 2350 𝑐𝑚−1 in the FTIR spectrum of cement or PAC-R additive with cement is an indicator of sample carbonation and the presence of CaCO3. This peak is usually observed in the FTIR spectrum of cement and is used for identification. The samples in Figure 16 c and Figure 17 have the same PAC-R concentration distribution in the content with different curing times.
The analogous tendency was observed in the studies of Lanka et al. 2021) with the extension of the curing time between the equivalent concentration of the EVA copolymer (Fig. 18).
Conclusion and recommendations
The effect of EVA on fresh properties of cement paste. Cement and Concrete Composites, 34(2), pp. 255-260. Physicochemical characterization of EVA-modified mortar and porcelain tile interfaces. Design of cement for completion of underground gas storage well. Journal of Natural Gas Science and Engineering, 18, pp. 149-154.
Action of redispersed vinyl acetate and versatile copolymer powder in cement mortar. Construction and Building Materials, 25(11), pp. 4210-4214. Effect of redispersed vinyl acetate and versatile copolymer powder on flexibility of cement mortar. Construction and Building Materials, 27(1), pp. 259-262. EVA modified cement for underground gas storage. Journal of Natural Gas Science and Engineering, 27, pp. 1846-1851.
Self-healing performance of EVA-modified cement for hydraulic fracturing wells. Building and construction materials, 146, p. 563-570.
