An Insight on Gas Migration in Cement Slurry

Abstract Cementing operations in deepwater exhibit many challenges worldwide due to shallow flows. Cement sheath integrity and durability play key roles in the oil and gas industry, particularly during drilling and completion stages. Cement sealability serves in maintaining the well integrity by preventing fluid migration to surface and adjacent formations. Failure of cement to seal the annulus can lead to serious dilemmas that may result in loss of well integrity. Gas migration through cemented annulus has been a major issue in the oil and gas industry for decades. Anti-gas migration additives are usually mixed with the cement slurry to combat and prevent gas migration. In fact, these additives enhance and improve the cement sealability, bonding, and serve in preventing microannuli evolution. Cement sealability can be assessed and evaluated by their ability to seal and prevent any leakage through and around the cemented annulus. Few laboratory studies have been conducted to evaluate the sealability of oil well cement. In this study, a setup was built to simulate the gas migration through and around the cement. A series of experiments were conducted on these setups to examine the cement sealability of neat Class H cement and also to evaluate the effect of anti-gas migration additives on the cement sealability. Different additives were used in this setup such as microsilica, fly ash, nanomaterials and latex. Experiments conducted in this work revealed that the cement (without anti-gas migration additive) lack the ability to seal the annulus. Cement slurries prepared with latex improved the cement sealability and mitigated gas migration for a longer time compared to the other slurries. The cement slurry formulated with a commercial additive completely prevented gas migration and proved to be a gas tight. Also, it was found that slurries with short gas transit times have a decent potential to mitigate gas migration, and this depends on the additives used to prepare the cement slurry.

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Gas Migration Prevention Using Hydroxypropylmethylcellulose as a Multifunctional Additive in Oil Well Cement Slurry

10.2118/169643-ms ◽

2013 ◽

Cited By ~ 2

Author(s):

Ghulam Abbas ◽

Sonny Irawan ◽

Sandeep Kumar ◽

Muhammad Nisar Khan ◽

Shuaib Memon

Keyword(s):

Oil Well ◽

Gas Migration ◽

Cement Slurry ◽

Multifunctional Additive ◽

Oil Well Cement ◽

Well Cement

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Recipe of Lightweight Slurry with High Early Strength of the Resultant Cement Sheath

Energies ◽

10.3390/en13071583 ◽

2020 ◽

Vol 13 (7) ◽

pp. 1583 ◽

Cited By ~ 5

Author(s):

Marcin Kremieniewski

Keyword(s):

Mechanical Performance ◽

Bonding Time ◽

Gas Migration ◽

Cement Slurry ◽

Well Drilling ◽

Filling Materials ◽

Cement Sheath ◽

Reliable Knowledge ◽

Short Time ◽

Geophysical Measurements

Admixtures of mineral or waste filling materials are used to reduce slurry density. However, the sheath made of lightweight cement slurry has low mechanical performance at the initial bonding time. The required strength is achieved later. This is the main problem when evaluating the cement bond logging. The waiting time for geophysical measurements after injecting and bonding of cement is nowadays increasingly shortened. This is forced by economic factors. Too early geophysical measurements may result in obtaining a false indication of the cement bond logging. The lack of cement or partial bonding, despite the presence of slurry in the annular space is then found. The slurry developed by the author achieves high compressive strength after a short bonding time. Reducing the amount of water in the slurry resulted in a lowered filtration value. This is important in preventing gas migration after the cementing. The designed slurry also reaches the value of 3.5 MPa in a short time. This allows for an earlier commencement of a well drilling. The use of said slurry improves the effectiveness of the well sealing and makes it possible to obtain a reliable knowledge of the bond logging.

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Badania procesu żelowania zaczynów cementowych przeznaczonych do uszczelniania otworów przewiercających płytkie poziomy gazonośne

Nafta-Gaz ◽

10.18668/ng.2021.04.03 ◽

2021 ◽

Vol 77 (4) ◽

pp. 235-243

Author(s):

Marcin Rzepka ◽

◽

Miłosz Kędzierski ◽

Keyword(s):

Hydrostatic Pressure ◽

Oil And Gas ◽

Gel Strength ◽

Gas Migration ◽

Annular Space ◽

Cement Slurry ◽

National Research Institute ◽

Shallow Gas ◽

High Molecular Weight Polymer ◽

Research Institute

The article presents issues related to the sealing slurry technology concerning gelling processes (i.e., static built-up of gel strength of cement slurries). Based on research conducted around the world, it can be concluded that the rate of gelling of the cement slurry has an important role in the process of preventing possible gas exhalations from the annular space. After the cement slurry is pumped into the borehole (especially in zones with shallow gas horizons), the so-called migration (exhalation) of the formation medium (i.e. uncontrolled outflow of e.g. gas from the annular space) may occur. The most important caused of gas migration from the shallow horizons after casings cementation are the inability to maintain a certain overpressure by the column of the binding cement slurry and too long binding of the cement slurry after pumping into the borehole. The initially liquid cement slurry, when pumped out of the casing, acts as a liquid, creating a certain hydrostatic pressure on the deposit. e.g. gas. However, after some time, the period of building the static gel strength (SGS) starts until the cement sets. The SGS building process, i.e. gelling of the cement slurry, reduces the ability to transmit hydrostatic pressure to the reservoir. The Oil and Gas Institute – National Research Institute has tested a number of cement slurry formulations characterized by different gelling and bonding times. Slurries were made on the basis of three typed of latex with the symbols L1, L2, L3, two types of water glass with symbols S1, S2, amorphous silica with the symbol CB, nano-components based on n-SiO2 and n-Al2O3 with the symbols NS and NA as well as high-molecular weight polymer with the symbol GS. Different amounts of setting accelerator were used with the tested slurries. Tests were carried out for eighteen cement recipes, which made it possible to select the optimal compositions of slurries with short gelling and setting times. The samples containing one of the types of latex in the appropriate concentration, the GS polymer, as well as those containing n-SiO2 and n-Al2O3, showed a very advantageous course of the gelation plot (static build-up of gel strength). Their TT transition times, reflecting the course of gelation, ranged from several to several tens of minutes (which is a proof of high ability to prevent gas migration from shallow gas accumulations). The cement slurries developed at the Oil and Gas Institute – National Research Institute, due to their good technological parameters, could be used in the process of cementing casing strings.

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Reduction of fluid migration in well cement slurry using nanoparticles

Oil & Gas Science and Technology – Revue d’IFP Energies nouvelles ◽

10.2516/ogst/2020044 ◽

2020 ◽

Vol 75 ◽

pp. 67

Author(s):

Mahmoud Bayanak ◽

Soroush Zarinabadi ◽

Khalil Shahbazi ◽

Alireza Azimi

Keyword(s):

Fluid Migration ◽

Oil Well ◽

Gas Migration ◽

Test Results ◽

Cement Slurry ◽

Negative Effects ◽

Transient Time ◽

Well Completion ◽

Nanosilica Particles ◽

Well Cement

One of the main problems during oil well completion and cementing operation is fluid migration through cement bulk or behind the cemented casing. Slurry composition and characteristic have been focused and improved in last decades to mitigate gas migration and, recently, aspects such as using nanotechnology have been investigated to amend the conditions. In this research, two moderate base slurries with 95 and 120 Pound per Cubic Feet (PCF) densities containing different percentages of nanosilica have been examined using a perfect test package. The results of Fluid Migration Analyzer (FMA) demonstrated that using correct percentage of nanosilica particles modified rheological behavior of the slurries and decreased fluid migration volume. Moreover, adding nanoparticles did not have any negative effects on any conventional parameters. However, static gel strength analyzer showed significant transient time reduction which is an important key in cement setting profile. Triaxial test results together with Mohr circles analyzing presented considerable progress in cement stability and compressive strength.

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A Review of Rheological Modeling of Cement Slurry in Oil Well Applications

Energies ◽

10.3390/en13030570 ◽

2020 ◽

Vol 13 (3) ◽

pp. 570 ◽

Cited By ~ 6

Author(s):

Chengcheng Tao ◽

Barbara G. Kutchko ◽

Eilis Rosenbaum ◽

Mehrdad Massoudi

Keyword(s):

Yield Stress ◽

Constitutive Modeling ◽

Oil Well ◽

Rheological Characteristics ◽

Gas Migration ◽

Cement Slurry ◽

Water To Cement Ratio ◽

Thixotropic Behavior ◽

Temperature And Pressure ◽

Rheological Modeling

The rheological behavior of cement slurries is important in trying to prevent and eliminate gas-migration related problems in oil well applications. In this paper, we review the constitutive modeling of cement slurries/pastes. Cement slurries, in general, behave as complex non-linear fluids with the possibility of exhibiting viscoelasticity, thixotropy, yield stress, shear-thinning effects, etc. The shear viscosity and the yield stress are two of the most important rheological characteristics of cement; these have been studied extensively and a review of these studies is provided in this paper. We discuss the importance of changing the concentration of cement particles, water-to-cement ratio, additives/admixtures, shear rate, temperature and pressure, mixing methods, and the thixotropic behavior of cement on the stress tensor. In the concluding remarks, we propose a new constitutive model for cement slurry, considering the basic non-Newtonian nature of the different models.

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Solid Polymer Prevents Gas Migration into Cement Slurry in Subzero Conditions (Russian)

10.2118/166853-ru ◽

2013 ◽

Author(s):

Islam Isgenderov ◽

Martijn Bogaerts ◽

Kevin Docherty ◽

Victor Osayande

Keyword(s):

Solid Polymer ◽

Gas Migration ◽

Cement Slurry

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Comparison of Efficient Ways of Mud Cake Removal from Casing Surface with Traditional and New Agents

Energies ◽

10.3390/en14123653 ◽

2021 ◽

Vol 14 (12) ◽

pp. 3653

Author(s):

Marcin Kremieniewski ◽

Rafał Wiśniowski ◽

Stanisław Stryczek ◽

Paweł Łopata

Keyword(s):

Reference Sample ◽

Gas Flows ◽

Gas Migration ◽

Annular Space ◽

Cement Slurry ◽

Rotational Viscometer ◽

New Agents ◽

Mud Cake ◽

Rotor Surface ◽

Cake Removal

The tightness of the casing-rock formation interface is one of the most important elements of drilling and cementing jobs. In the absence of the required tightness, there is a risk of gas migration directly to the ground, groundwater or atmosphere. In order to eliminate this type of uncontrollable and unfavorable gas flows, the casing column is sealed with cement slurry in the annular space or beyond casing. Cement slurry displaces mud present in the annular space, although the mud cake cannot be completely removed, which is required for obtaining proper binding of cement slurry with the casing surface and the surface of the drilled formation. Therefore, it is important to prepare the well and remove the mud cake from the annular space with spacer fluid. An occasional lack of wellbore tightness requires continuous improvement of the cementing technology. Accordingly, analyses are conducted on mud cake removal with modified or new spacer fluids. Properly designed fluid should efficiently clean the surface of the casing and of the rock mass. One of the basic measurements is the analysis of the efficiency of mud cake removal from the surface of a rotational viscometer. The efficiency of traditional and newly designed fluids for mud cake removal from the casing surface with new and traditional agents has been compared further in this paper. The methodology of mud cake removal with the use of a rotational viscometer was also presented. Tests were performed for various concentrations of agents already used for spacer fluids and for a group of new agents. The efficiency of annular space cleaning was determined on the basis of a comparison with the results obtained for the reference sample, i.e., water which was used for mud cake removal from the rotor surface. The analysis of the results of experiments created bases for the comparison of the efficiency of the analyzed spacer fluids and finding the most suitable ones for mud cake removal from casing columns.

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A Novel Approach to Successfully Cement the Long Horizontal Liners Across Khuff-C Reservoir in High-Pressure Gas Producer Land Wells: A Case History from Saudi Arabia

10.2523/iptc-21335-ms ◽

2021 ◽

Author(s):

Wajid Ali ◽

Freddy Jose Mata ◽

Faisal Abdullah Al-Turki

Keyword(s):

Drilling Fluid ◽

Horizontal Wells ◽

Gas Migration ◽

Cement Slurry ◽

Oil Companies ◽

Temperature Modeling ◽

Novel Approach ◽

Open Hole ◽

Zonal Isolation ◽

Testing Field

Abstract Maintaining zonal isolation is vital to well economics and productive life. Well integrity is becoming more challenging with the drilling of deeper, highly deviated, and horizontal wells worldwide. Oil companies are focused on to enhance the well productivity during drilling long horizontal wells in a harsh environment by achieving maximum accessible reservoir contact. These wellbore geometries incorporate additional challenges to design and deliver a dependable barrier. In this paper, a case study about cementing the longest liner across Khuff-C reservoir has been presented discussing the main challenges, engineering considerations, field implementation, results, and conclusions. The well was drilled horizontally across Khuff-C carbonates using oil-based drilling fluid. The 5-7/8-in open hole section was planned to be cemented in single stage, utilizing 8370 ft of a 4-1/2-in liner. Careful attention was paid to estimate the bottom hole circulating temperature, using the temperature modeling simulator. A 118-lbm/ft3 slurry was designed to keep the equivalent circulation density intact. Gas migration control additives were included in the slurry design to lower the slurry's transition time, in order to reduce the chances of gas migration through the cement slurry. The slurry was batch-mixed to ensure the homogeneity of the final slurry mixture. A reactive spacer was designed to improve the cement bonding from long term zonal isolation perspective. Additionally, the spacer was loaded with optimum amounts of surfactant package to serve as an aid to remove the mud and to water-wet the formation and pipe for better cement bonding. Centralizers placement plan was optimized to allow around 63% average standoff around the pipe, staying within the torque and drag (T&D) limits. The cement treatment was performed as designed and met all zonal isolation objectives. The process of cementing horizontal liners comes with unique procedures. There are several challenges associated with carrying out wellbore zonal isolation for primary cementing of horizontal liners, therefore, a unique level of attention is required during the design and execution stages. The slurry design requires careful formulation to achieve the desired specifications while ensuring its easy deployment and placement in the liner annulus. By planning in advance and following proven techniques, many of the problems associated with the running and cementing of deep and long horizontal liners can be alleviated. This paper highlights the necessary laboratory testing, field execution procedures, and treatment evaluation methods so that this technique can be a key resource for such operations in the future. The paper describes the process used to design the liner cement job and how its application was significant to the success of the job.

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