The Effect of Weighting Materials on Oil-Well Cement Properties While Drilling Deep Wells

The Effect of Olive Waste on the Rheological Properties, Thickening Time, Permeability, and Strength of Oil Well Cement

In the oil and gas industry, cementing is a very important process to maintain the stability of the well. The cement can provide an effective plug against fluid movement and at the same time supports the casing and formations. Based on the operation conditions, different types of additives are used to make the cement slurry, and incorporation of a new additive considerably affects all properties of the cement slurry and the solidified sheath. In this work, lab experiments were performed to investigate alteration of the Saudi Class G cement properties after incorporation of olive waste into the slurry, and the possibility of replacing the commercial retarder with olive waste was also studied in this work. Five samples with different olive waste content were prepared, and their rheological characteristics, thickening time, mechanical properties, and permeability were evaluated after 24 h of curing at 95 °C. The results indicated that olive waste could replace the use of a commercial retarder. The incorporation of olive waste did not affect the cement plastic viscosity, while the yield point, 10 s, and 10 min gel strengths of the cement were considerably increased with the increase in the olive waste content. The cement compressive strength was also increased with the incorporation of olive waste of a maximum of 0.375%, and the permeability decreased with the addition of a maximum of 0.25% olive waste.

Development of Heavy-Weight Hematite-Based Geopolymers for Oil and Gas Well Cementing

In the petroleum industry, ordinary Portland cement (OPC) is utilized for different cementing applications. Yet, there are some technical and environmental issues for the usage of OPC in well cementing. The technical problems include gas invasion while setting, instability at corrosive environments, cement failure while perforation and fracturing due to high stiffness and brittleness, and strength reduction and thermal instability at elevated temperatures. Moreover, OPC production consumes massive energy and generates high greenhouse gas emissions. This study introduced the first hematite-based class F fly ash geopolymer formulation that can be used in oil and gas well cementing. Different properties of the designed slurry and hardened samples such as rheology, thickening time, strength, and elastic and petrophysical properties were evaluated. Moreover, mixability and pumpability challenges of heavy-weight geopolymer slurries were investigated. Unlike most of the studies in the literature, this work used 4 M NaOH solution only as an activator that can reduce the overall cost. The results showed that increasing the hematite percentage significantly decreased the thickening time. The developed formulation fell within the recommended fluid loss ranges for some cementing applications without using a fluid loss control additive. A proposed mixture of retarder and superplasticizer was introduced to enhance the thickening time by almost 5 times. The compressive strength increased by 49% and the tensile strength was enhanced by 27.4% by increasing the curing time from 1 to 7 days. The improvement in both compressive and tensile strength with curing time indicated that the geopolymerization reaction continued for extended time but with a smaller rate. The developed slurry acted more like a power law fluid at low temperatures and more like a Bingham plastic fluid at high temperatures. The elastic properties of the developed geopolymer samples proved that they are more flexible than some cement systems.

Effect of Graphite on the Mechanical and Petrophysical Properties of Class G Oil Well Cement

Casing cementing is one of the most crucial operations in the oil well drilling process since it determines the durability and stability of the well throughout its life. Different additives have been mixed into the oil well cement slurry to improve the properties of both the cement slurry and the solidified cement sheath. Graphite is a waste material with a huge potential to be utilized in cementing to improve the properties of the oil well cement and reduce the graphite waste content in the environment. This study intends to analyze the effect of graphite on alteration in properties of the cement compressive and tensile strength, Poisson's ratio, Young's modulus, porosity, and permeability for three days of curing. Based on the trend of the properties during the three days of curing, equations were established to describe the future change in cement properties with time. Two formulas of cement, the base (with no graphite) and graphite-based (with 0.2% by weight of cement graphite) were prepared in this study. The results showed that the graphite successfully increased the compressive strength, tensile strength, and Poisson's ratio of the cement sheath, throughout the curing process. Young's modulus was decreased after the incorporation of graphite which indicates an enhancement in cement resistance to shear forces. The porosity and permeability were also decreased indicating formation of a more densified cement sheath.

Effect of using Austrian pine cones powder as an additive on oil well cement properties

There have been many investigations to improve both the physical and mechanical properties of oil well cement using a wide range of materials. Most of these additives are expensive and practically ineffective. In this article, a comprehensive evaluation was conducted for using Austrian pinecones powder (APCP) as an inexpensive supplementary cementing material (SCM) for well cement. Firstly, Portland cement class G was characterized based on X-Ray Fluorescence (XRF), X-Ray Diffraction (XRD). In this paper, the properties of the cement systems include rheological parameters, density, slurry stability (free water test, and sedimentation test), water absorption, porosity, permeability, the volume of fluid loss, pH value, thermogravimetric analysis, and the mechanical characteristics (in terms of compressive strength, tensile strength, flexural strength, and shear strength bond) were investigated in details. The cement sample containing the APCP was also examined using scanning electron microscopy (SEM). According to the experimental results, adding APCP led to increasing in rheological parameters. Also, led to decreasing in fluid loss, free water, sedimentation effect, and density which positively affects the preservation of the original properties of cement slurry. The results also showed a decrease in the permeability of cement samples and an increase in the porosity and the ability to absorb water. The addition of APCP did not significantly affect the pH values. The addition of APCP also deteriorated the mechanical properties of the cement samples. The addition of the APCP has contributed to an increase in total weight loss at high temperatures. So, the APCP can be considered as a new filler for well cement due to its ability to fill the pores in the cement matrix and at the same time improve some properties of the well cement such as density, free water, sedimentation, and fluid loss.

Research on Key Technologies to Improve Cementing Displacement Efficiency

The annulus has a wide and narrow clearance due to casing eccentricity in the cementing process and due to the eccentricity of casing in the process of cementing. Because the flow resistance of the drilling fluid in the wide gap is less than that in the narrow gap, the phenomena of a delayed flow or even an overall nonflow occurs in the narrow gap. Based on the existing displacement efficiency calculation model, this paper establishes the cementing displacement efficiency model under the condition of oil-based drilling fluid, explores the residual layer thickness of drilling fluid on the casing side and the sidewall side, and then links the annular displacement efficiency to the injection displacement in combination with the circulating mode resistance pressure drop formula so as to explore the change in the cementing displacement efficiency under different displacements. Considering the change in the physical parameters of annulus fluid, the change in annulus displacement efficiency is obtained. On this basis, the relationship between the wellhead cement injection flow and the annulus retention layer is studied; then, the displacement is calculated. The reasonable cementing displacement is calculated by combining the displacement with annulus displacement efficiency. The results show that the thickness of the annular detention layer increases with the increase in the casing eccentricity in the same well depth, and the growth rate of the detention layer on the wellbore side is greater than that on the casing side at the same circumferential angle. The greater the displacement, the greater the annular circulation pressure drop and circulation equivalent density, thus increasing the cementing risk. The displacement is reasonably designed. The research results in this paper have a certain guiding significance for improving the displacement rate of isolation fluid under oil-based drilling fluid conditions.

Optimization of Cement–Rubber Composites for Eco-Sustainable Well Completion: Rheological, Mechanical, Petrophysical, and Creep Properties

To ensure well integrity, wellbore must be strongly cased using durable cement slurries with essential additives during downhole completion. The rubber materials that come from industrial waste are becoming extremely encouraged in the use as an additive in preparing cement slurries due to their growing environmental footprint. However, the proper design of cement slurry strongly depends on its rheological, mechanical, petrophysical, and creep properties, which can be altered by changing additives. This study aimed to examine the cement properties under alteration in different chemical admixtures to create efficient binding properties, and to estimate the optimum cement–rubber slurry composition for eco-sustainable completion. Three cement samples with different mesh sizes of the crumb rubber particles were prepared. This study examined the variation in rheological behaviors, elastic and failure characteristics, permeability, and creep behavior of the cement–rubber composites for petroleum well construction. The experimental study showed that the addition of 15% or more crumb rubber to the cement resulted in very thick slurries. Moreover, it was shown that the addition of crumb rubber with various particle sizes to the cement reduced the strength by more than 50%, especially for a higher amount of rubber added. It was also revealed that the addition of a superplasticizer resulted in an 11% increase in compressive strength. The results showed that cement–crumb-rubber composites with 12% by weight of cement (BWOC) represented the optimum composite, and considerably improved the properties of the cement slurry. Water-permeability tests indicated the addition of 12% BWOC with 200-mesh crumb rubber decreased the permeability by nearly 64% compared to the base cement. Creep tests at five different stress levels illustrated that the neat cement was brittle and did not experience strain recovery at all stress levels. Cement slurries with the largest rubber-particle size were elastic and demonstrated the highest amount of strain recovery. Finally, a relationship was established between the permeability, average strain, and mesh size of the rubber particles, which offered the strain recovery, satisfied the zonal isolation, and consequently reduced the microannulus problem to ensure the cement’s integrity.

Increasing the Efficiency of Sealing the Borehole in Terms of Spacer Pumping Time

The tightness of a borehole is essential for its long-term durability. For this purpose, the column of the pipe is sealed with cement slurry. After contacting the slurry, mud in the borehole is removed. However, the slurry does not effectively remove the remaining drilling mud. Therefore, the annular space is cleaned with a wash. Effectively cleaning the borehole presents quite a problem, as many variables that affect the stability of the borehole need to be considered. The time of contact between the borehole and the wash is very important. On the one hand, insufficient contact time does not guarantee proper removal of the mud. On the other hand, a long contact time may destroy the wall of the borehole. To address these problems, studies were carried out to assess the effect of the wash contact time on annular space cleaning. When determining the time of washing, a compromise between effective cleaning and the stability of the borehole wall is required. In the research presented in this publication, the simplest wash was used, i.e., water. This choice was based on the objective of observing the influence of the wash time on cleaning, i.e., the preparation of the borehole for cementing. By using water, the physicochemical action of surfactants can be ignored. In order to capture changes in cleaning due to differences in contact time, a control test was performed using a pure sandstone core without mud. The effect of the wash contact time on the cleaning of the annular space was investigated by determining the adhesion of the cement sheath to the rock core. First, mud was formed on the core, and then it was removed. By comparing the obtained adhesion to the reference sample, the effectiveness of the deposit removal was determined. On the basis of this research, the optimal wash contact time was determined.

Hybrid Washer Fluid for Primary Cementing

This article presents the results on the basis of which a new hybrid drilling washer fluid was designed. The use of fluid from such a drilling washer increases the mud-cake removal efficiency. Its operation is based on both chemical and mechanical removal of the mud cake. This article presents a group of agents and admixtures of various solid fractions, the appropriate selection of which enabled the design of a hybrid drilling washer fluid. The liquid has much better washing parameters than the drilling washers used so far. The tests were carried out in a drilling fluid flow simulator. A significant improvement in the scrubbing mud-cake removal efficiency resulted from the action of surfactants and fine-grained abrasive additives. Their proper concentration was also very important. The hybrid drilling washer fluid was designed on the basis of tests measuring the adhesion of the hardened cement slurry to the rock from which the previously produced mud was removed. In this way, the effectiveness of the washing liquids was determined. Upon analyzing the obtained results and correlating them with the reference samples, one can see a significant improvement in the efficiency of the removal of the drilling sediment by the hybrid drilling washer fluid. The hybrid drilling washer fluid is an innovative solution because it combines chemical and mechanical action in the removal of drilling fluid. Additionally, such a washing liquid has not been used so far.

Effect of Perlite Particles on Barite Cement Properties

Conventional heavy-weight oil and gas well cement systems formulated with barite exhibit high viscosities. Additionally, the heavy-weight powder tends to settle, causing density variation and disruption in the porosity of the hardened cement cores. Studies have shown that such problems can be mitigated by controlling the particle size distribution of the cement system. The main objective of this study is to evaluate the effect of perlite powder particles on the fluid and hardened properties of barite-based cement systems. Barite heavy-weight cement slurries containing 0, 1, 2, and 3% by weight of dry cement (BWOC) of perlite powder were prepared. The rheological study was performed at a bottomhole circulating temperature (BHCT) of 150 °F and ambient pressure. An ultrasonic cement analyzer (UCA) and a high-temperature-high-pressure (HTHP) curing chamber were used to cure samples for 24 h at a bottomhole static temperature (BHST) of 292 °F and pressure of 3000 psi. Porosity measurements were performed using the nuclear magnetic resonance (NMR) technique. The results indicate that the incorporation of perlite powder into conventional barite-based heavy-weight cement slurry causes modifications in the properties of the systems. In general, the plastic viscosity decreases, while the yield point and gel strength increase with increasing perlite concentration. The reduction in plastic viscosity also reduces the pump pressure, while the increase in yield point and gel strength reduces particle sedimentation. Additionally, the compressive strength and tensile strength of hardened cement increase, while the wait-on-cement time decreases. NMR studies indicate that perlite reduces the porosity variation that exists in conventional barite-based cement systems due to the formation of stable cement systems.

The Use of the Granite Waste Material as an Alternative for Silica Flour in Oil-Well Cementing

Silica flour is one of the most commonly used material in cementing oil wells at high-temperature conditions of above 230 °F to prevent the deterioration in the strength of the cement. In this study, replacement of the silica flour with the granite waste material at which an inexpensive and readily available material in cementing oil-wells is evaluated. Four cement samples with various amounts of silica flour and granite powder were prepared in this work. The effect of including the granite waste instead of silica flour in the cement elastic, failure, and petrophysical properties after curing the samples at 292 °F and 3000 psi was examined. The results revealed that replacement of the silica flour with 40% by weight of cement (BWOC) optimized the cement performance and confirmed that this concentration of granite could be used as an alternative to the silica flour in oil-well cementing. This concertation of granite slightly improved the elastic properties of the cement. It also improved the cement compressive and tensile strengths by 5.7 and 39.3%, respectively, compared to when silica flour is used. Replacement of the silica flour with 40% BWOC of granite waste also reduced the cement permeability by 64.7% and porosity by 17.9%.

Improving Saudi Class G Oil-Well Cement Properties Using the Tire Waste Material

After oil and gas well drilling, they should be cased and cemented to ensure the stability of the wellbore and to isolate the trouble zones. To achieve these jobs, several additives are incorporated into the cement slurry to improve the cement matrix durability, especially at temperatures above 230 F. The tire waste material is an industrial waste that comes from automobile tires. The purpose of this work is to investigate the prospect of utilizing tire waste in oil-well cement under high-temperature and high-pressure conditions of 292 F and 3000 psi. Three cement samples with different concentrations of the tire waste material were prepared. The effects of tire waste on the cement rheological properties, elastic and failure parameters, and permeability were examined. The results showed that adding 0.3% by weight of cement (BWOC) of the tire waste material considerably improved the cement to the cement slurry and cement matrix properties, and it decreased the cement plastic viscosity by 53.1% and increased its yield point by 142.4% compared to the base cement. The cement samples with 0.3% BWOC of tire waste have Young's modulus which is 10.8% less than that of the base cement and Poisson's ratio of 14.3% greater than that of the base cement. By incorporating 0.3% of the tire waste, both compressive and tensile strengths of the cement increased by 48.3 and 11.7%, respectively, compared with those of the base cement. The cement permeability was decreased by 66.0% after adding 0.3% of the tire waste. Besides the improvement in the properties of cement, the use of the tire waste material has other economical and environmental advantages because these are very cheap materials dominant in our life.

Influence of Weighting Materials on the Properties of Oil-Well Cement

The integrity of oil and gas wells is largely dependent on the cement job. Maintaining the properties of the cement layer throughout the life of a well is a difficult task, particularly in high-temperature and -pressure conditions such as those in deep wells. Cementing deep wells require slurries with high densities. Heavyweight cement systems are those designed with weighting materials. These materials have a higher specific gravity in comparison to cement. The purpose of this work is to investigate the influence of weighting materials on the properties of Class G oil-well cement and to make necessary recommendations for their use. The rheology, fluid loss, gas migration, and dynamic elastic properties of three cement slurries containing different weighting materials, namely, hematite, barite, and ilmenite, were studied. The results indicate that cement slurry designed with barite exhibits the best rheological behavior that would provide a perfect solution for deep wells where cement placement is a concern. The barite slurry had the lowest plastic viscosity. The plastic viscosity of the hematite and ilmenite-weighted systems was higher by 11.5 and 12.4%, respectively. The barite-based slurry also had the highest yield point of 84.3 lb_f/100 ft², whereas the yield points of hematite and barite cement were 37.9 and 29.5 lb_f/100 ft², respectively. Furthermore, the gel strengths of barite cement were the highest, with 10 s and 10 min gel strengths of 11.5 and 39.5 lb_f/100 ft², respectively. Ilmenite had the most positive impact on fluid loss control, which would be appropriate in high permeable formations. It had a fluid loss of 66 mL/30 min, lower than those of the hematite (80 mL/30 min) and barite (82 mL/30 min) systems. Furthermore, the best dynamic elastic properties were exhibited by the ilmenite system, with the smallest Young's modulus (27.3 GPa) and the highest Poisson ratio (0.252). This would make the ilmenite to be very useful in developing heavyweight cement composites that could withstand severe external loads imposed on the casing and cement. The hematite cement was the most impermeable to gas migration, with a gas volume of 127.8 cm³, whereas the volume measured in the barite and ilmenite systems were 20.9 and 78% higher, respectively. This makes the hematite to be very useful in deep gas wells where gas migration control is important.

Influence of Graphene Oxide on Rheological Parameters of Cement Slurries

In recent years, graphene-based nanomaterials have been increasingly and widely used in numerous industrial sectors. In the drilling industry, graphene oxide in cement slurry has significantly improved the mechanical parameters of cement composites and is a future-proof solution. However, prior to placing it in a borehole ring space, cement slurry must feature appropriate fluidity. Graphene oxide has a significant influence on rheological parameters. Therefore, it is necessary to study graphene oxide’s influence on the rheological parameters of cement slurries. Thus, this paper presents rheological models and the results of studies on rheological parameters. A basic cement slurry and a slurry with a latex addition were used. The latex admixture was applied at concentrations of 0.1%, 0.03%, and 0.06%. In total, studies were carried out for six slurries with graphene oxide and two basic slurries. The obtained results of studies on the slurries with graphene oxide were compared with the control slurry. It was found that the smallest graphene oxide concentration increased slurry value, some rheological parameter values, plastic viscosity, and the flow limit. Surprisingly, a concentration up to 0.03% was an acceptable value, since the increase in plastic viscosity was not excessively high, which allowed the use of cement slurry to seal the hole. Once this value was exceeded, the slurry caused problems at its injection to the borehole.