Cementing Of Oil Wells Research Articles

Oil-well lightweight cement slurry for improving compressive strength and hydration rate in low-temperature conditions

Inadequate early compressive strength is a common problem when employing lightweight cement (LWC) slurries during the cementing of oil wells under low-temperature conditions. A new formulation of LWC slurry was investigated by the Research Institute of Petroleum Industry (RIPI) to improve the compressive strength and hydration rate of LWC slurries in low-temperature conditions. In this study, bottom-hole static temperature (BHST) ranges from 21 °C to 82 °C. Halliburton cement friction reducer (CFR-3), Litefil microspheres (D-124), hydroxy ethyl cellulose (D-112), styrene butadiene latex (D-600), and high strength hydrophobic silica (HSL-2) were as lightweight additives to make the RIPI-LWC formulation. The results showed that adding more 5 g of HSL-2 nanoparticles causes in a low-density cement slurry from 1442 kg/m3 to 1281.5 kg/m3. Besides, at the temperature of 21 °C, the strength value (i.e., 3.5 MPa @ 3:56 h)) was developed much faster than the temperature of 82 °C (i.e., 3.5 MPa @ 20:48 h), providing more significant insights into applying the proposed lightweight cement by reducing curing time. Furthermore, the hydraulic bonding of cement slurry was increased by attention to the action of thixotropic additive in preventing the gas migration from the cement slurry. The involvement of the new RIPI-LWC implies that cement columns can be pumped higher in the annulus, multiple-stage cementing becomes unnecessary without reducing cement integrity, and it is more economical and cost-effective than previous RIPI formulations.

Displacement flows in eccentric annuli with a rotating inner cylinder

We experimentally study the effects of inner cylinder rotation on the displacement flow of two Newtonian fluids along a horizontal eccentric annulus, with differing viscosities and densities. With the rotation of the inner cylinder, the flow behavior changes from stratified to helical, as rotation dominates buoyancy, or directly to an azimuthally dispersive regime when rotational velocity dominates axial velocity. Flow separation is observed to occur when eccentricity is high: the displacing fluid is contained in the wide gap of the annulus, and the effective displacement is delayed. Rotation is effective in creating azimuthal flow in the narrow gap, where there is limited flow and bottom-side residual fluid may be present. In most cases, rotation improves the displacement (volumetric efficiency) by shortening the length of the axial elongation of the displacement front, and eventually, steady displacements are seen. The study is motivated by displacement flows occurring during the primary cementing of long horizontal oil and gas wells. Rotating the inner cylinder (casing) is recommended. Our results suggest that this practice increases azimuthal dispersion and can prevent a narrow mud channel from forming if the excess fluid volume is used.

Comparative analysis of the geopolymer and Portland cement application as plugging material under conditions of incomplete displacement of drilling mud from the annulus

Portland cement is traditionally used in cementing of oil and gas wells. However, Portland cement has a number of shortcomings. The most important of these are the formation of microannuli between the cement plug and the rock or casing, as well as the formation of cracks and permeable channels in the cement matrix. Recent research shows that geopolymer can be a perspective alternate to portlandcement by overcoming beforementioned issues. The article comparatively analyzes the changes in the parameters of plugging materials containing geopolymer and Portland cement while contamination with water-based drilling mud. The results show that geopolymerbased solutions are more resistant to contamination with water-based drilling mud than Portland cement-based solutions. Thus, mixing Portland cement slurry with water-based drilling mud increases its viscosity and fluid loss, and sharply reduces its compressive strength. However, when a geopolymer solution is mixed with a water-based drilling fluid, its viscosity is almost unchanged, its fluid loss is reduced, and reduction in its compressive strength is less than in Portlandcement based material. Keywords: portland cement; geopolymer; fly ash; cementing; water based mud; mud contamination.

Isolation cementing of oil and gas wells of the Сarpathian region

The problem of reliable isolation cementing of oil wells belonging to non-operating stock is considered. It is shown that the oil and gas fields of the Carpathian region are characterized by unique mining, geological and geographical conditions, as well as a large number of old wells of complex design that require unconventional solutions when performing isolation works. The peculiarities of structure formation, technological properties of insu-lating materials based on oil well cement PCT I-100 and composite mixtures CREA, CREA-LF have been studied. It was found that in the first case, the hydration products are represented by ettringite, hexagonal AFm phases, calcium hydroxide and fibrous hydrosilicates. The following phenomena are characteristic for composite materials: a more uniform distribution of hydrates in the gel mass of hydrosilicates, better ordering of the contact zones of accretion, and an increase in the number of intergrown fibers in blocks of hydrosilicates. All of that ensures the formation of a stone of a denser structure, the closure of a larger number of hydrates surface active centers in contact interactions, controlled synthesis, improvement of the strength characteristics and deformation properties of the cement stone. It is shown that the improvement of the quality of composites is facilitated by the use of modern polyfunctional additives-modifiers applying the technology of manufacturing dry building mixtures. It has been found that to increase the efficiency of krents, it is advisable to use complex additives of multifunctional action, which, complementing each other, make it possible to achieve an additive and sometimes synergistic effect. A new generation plasticizer based on polycarbonates, stabilizing additives and micro-reinforcing fibers is used as a modifier of the CREA and CREA-LF composite mixtures. The ability to microplastic deformation of the composite matrix, reinforced by microreinforcement, causes higher energy consumption for the destruction of the stone. An improved technology for performing insulation works is proposed, taking into account the design features and the state of well support elements, which provides for the use of thermographenite and zeolite tuff in addition to the binder material.

Experimental Methods for Investigation of Drilling Fluid Displacement in Irregular Annuli

Experimental methods are still indispensable for fluid mechanics research, despite advancements in the modelling and computer simulation field. Experimental data are vital for validating simulations of complex flow systems. However, measuring the flow in industrially relevant systems can be difficult for several reasons. Here we address flow measurement challenges related to cementing of oil wells, where main experimental issues are related to opacity of the fluids and the sheer size of the system. The main objective is to track the propagation of a fluid-fluid interface during a two-fluid displacement process, and thereby to characterize the efficiency of the displacement process. We describe the implementation and use of an array of electrical conductivity probes, and demonstrate with examples how the signals can be used to recover relevant information about the displacement process. To our knowledge this is the most extensive use of this measurement method for studying displacement in a large-scale laboratory setup. Optical measurements and visual observations are challenging and/or costly in such large-scale systems, but can still provide qualitative information as shown in this article. Using electrical conductivity probes is a robust and fairly low-cost experimental method for characterizing fluid-fluid displacement in large-scale systems.

Turbulent displacement flow of viscoplastic fluids in eccentric annulus: Experiments

We study displacement flows in strongly eccentric annuli, where the in situ fluid is viscoplastic and the displacing fluid is Newtonian. This mimics the situation found in the cementing of horizontal oil and gas wells. In this configuration, it is common that the yield stress of the displaced fluid prevents displacement from the narrow side of the annulus, where it remains static. We address the question of whether a turbulent flow of the displacing fluid will be effective in removing the static narrow side channel and by what means. The flows proceed with rapid displacement along the wide side of the annulus, leaving behind a gelled channel of fluid on the narrow side. The narrow side is displaced either slowly or not at all. This depends on both the yield stress of the displaced fluid and the turbulence characteristics of the displacing fluid. We influence the latter through the use of drag-reducing polymers. We show that secondary flows in the turbulent displacing fluid are essential to the displacement and also the increased pressure drops in the turbulent flow. We hypothesize that the displacement is enhanced by the transmission of normal stresses into the gelled layer.

ЛЕКСИКО-СЕМАНТИЧНІ ОСОБЛИВОСТІ АНГЛІЙСЬКОЇ ТЕРМІНОЛОГІЇ НАФТОГАЗОВОЇ СФЕРИ

The lexical-semantic features of the English terms of oil and gas sphere are considered. Attention is drawn to the phraseological and metaphorical features that are characteristic of the terms of the oil and gas industry. It has been revealed that English oil and gas terminology is built on a heterogeneous model, that is, the result of the interaction of several areas of human knowledge. It includes geological, geophysical, geochemical terms, as well as terms related to drilling, washing, fastening and cementing of oil and gas wells, development of oil and gas fields, underground hydraulics, oil and gas production, processing methods, pipeline terminology, offshore drilling terminology, economic terminology. It is has been found out that the semantic categories of English oil and gas terminology are evidence that the terminology under study reflects a particular sphere of human activity that can be structured in some way by the means of language. In this process, the human factor is important. On the one hand, it is inherent in each of the categories, and serves as a basis for subjectivity in identifying the peculiarities of the content.The semantic categories of English oil and gas terminology are analyzed. These include: Human, Process, Equipment, Substance, Method, and Characteristics. The study showed that among the English oil and gas terms formed by metaphorization, we can distinguish terms conventionally grouped under the following lexical-semantic groups: “Parts of the human body”, “World of animals and birds”, “Clothes”, “Society”, “Cooking”, “Construction”, “Nature”, “Traveling”, “Weapon”, “Tool”, “Geometric figure”, “Hunting”, “Fishing”, “Medicine”, “Furniture” та “Quality”.

Laboratory study of additional use nano silica composite and bagasse ash to improve the strength of cement drilling

The effect of increasing cement prices and expensive additive will have an impact on the cost of cementing of oil and gas wells. So, the need for a strategy undertaken in order to minimize the cost of cementing other than that a good cement strength with additive alternative materials is necessary. Strategies are carried out by using materials that are economical and environmentally friendly in which the material is organic waste materials that have elements of silica and are pozzolanic. As for organic ingredients that are pozzolanic is bagasse ash. In addition, to reduce the level of cement pores, it is necessary to add additional additives by using nanosilica. Testing of the physical properties of cement conducted in laboratory research is by testing strength on cement with additives of bagasse ash added nanosilica into drilling cement suspension with temperature conditioning research 120°F pressure 14.7 psi and 24 hours in the water bath. The results of the research on several scenarios of the concentration of the addition of bagasse ash showed that the optimal compressive strength value obtained was 991.83 psi and the optimal shear bond strength obtained was 97,49 psi at the concentration of ash bagasse in 5% and nanosilica 0,019% in drilling cement.

Turbulent displacement flows in primary cementing of oil and gas wells

There is a widely popular perception in the cementing community that the turbulent regime should be used where possible in primary cementing of oil and gas wells. We conduct a detailed numerical study and analyze turbulent annular displacement flows. In particular, we show what roles viscous and buoyancy stresses play in the displacement efficiency. More importantly, we argue that the long-standing industry practice of preferring a turbulent displacement flow over laminar is over-simplistic and questionable. Indeed, we demonstrate that if the flow rate is increased very much when turbulent, steady displacements will be lost.

A model for foamed cementing of oil and gas wells

We present a two-dimensional model of the primary cementing process for foamed cement slurries. Foamed cement slurries have a number of claimed advantages, but also have a pressure-dependent density and rheology. The rheology is hard to quantify fully over all ranges of foam quality, which compromises the accuracy of models. The density variation is due to expansion/compression of the gas phase along the well, caused by variations in the static pressure. We show that in the absence of careful control, buoyancy-driven instabilities can result in the annulus, as the foamed slurry expands and the density drops below that of the displaced drilling mud. These instabilities appear to be of a classic porous media/Hele-Shaw cell fingering type, triggered by a threshold unstable density difference. We show that these instabilities are amplified by wellbore eccentricity, occurring lower in the well than in a concentric annulus. Our results question the safe usage of foamed cements in primary cementing.

Tracking fluid interfaces in primary cementing of surface casing

We present a new method to track the interface between two fluids in an annular displacement flow typical of setting surface casing in the primary cementing of oil and gas wells. The main idea is to exploit the density difference between successive fluids pumped in order to design a tracer particle to sit at the interface. Although apparently trivial, such particles must overcome viscous drag and strong secondary flows in order to reach and remain at the interface. We explore the underlying physics through both a simple toy model and using a full annular displacement simulation. The study provides a proof of concept that the method can work, but also exposes some limitations in terms of cementing parameters and particle properties. As well as demonstrating feasibility, we explore how some of these limitations might be overcome.

Buoyancy effects on micro-annulus formation: Density unstable Newtonian–Bingham fluid displacements in vertical channels

Buoyant miscible displacement flow of a Bingham fluid by a Newtonian fluid along a vertical plane-channel is studied, in the high Péclet number regime. The displacing fluid is lighter than the displaced fluid and the flow direction is upwards, hence density-unstable. The flow is effectively governed by 4 dimensionless parameters: the Newtonian Bingham number (BN), the viscosity ratio (m), the Reynolds number (Re), and modified Froude number (Fr). This is a simple model for micro-annulus formation in the primary cementing of oil and gas wells. The micro-annulus layers correspond to residual drilling mud that remains on the walls after displacement. Here we show that in density unstable situations static residual wall layers can exist for yield stresses below the minimum for density stable regimes. The layers are partially static and may also be thicker than the fully static layers encountered in density stable flows. Adverse buoyancy gradients (represented here by large χ=2ReFr2), also seems to promote instability of the flow. These instabilities are various, ranging from Rayleigh–Taylor type frontal instabilities, through to Kelvin–Helmholz type inertial waves, and more viscous-controlled inverse bamboo and mushroom morphologies. We present an overview of flow regimes within our parameter space and approximate onset criteria. It is unclear whether or not the instabilities observed result in improved fluid displacement efficiency.

A novel method to investigate cement-casing bonding using digital image correlation

The main focus of current industry practices on the cementing of oil and gas wells is short-term cement-design goals such as high strength, adequate pumpability and proper placement of cement in the wellbore. However, the bond between cement and casing is a major factor for long-term integrity of wellbore which requires more attention with the current increasing trend in horizontal drilling and hydraulic fracturing operations in unconventional resources. These wells experience various kinds of forces throughout their life in which the casing and cement bond can play a critical role in the integrity or failure of these wells. In this paper, we apply digital image correlation (DIC) technique to monitor strain development over the surface of a casing filled with cement while it is diametrically compressed. In this technique, the casing/cement sample is painted with random white and black speckles and the surface of sample is recorded by camera. Finally, strain development with time is calculated using image processing technique. This visualization helps to find out the points of weakness for strain accumulation which eventually end up for fracture initiation and propagation. In this laboratory setup, the tensile strain accumulation is the highest on the casing/cement interface 90-degree away from casing/loading point and the strain gradually increases at the casing/cement interface toward the casing/loading point. Then there is fracture generation at the center of cement sample propagating toward casing/loading point. We also review the impact of cement contamination, barite and water-cement ratios on cement/casing bonding and their associated DIC results.

Primary cementing of oil and gas wells in turbulent and mixed regimes

We present a detailed derivation of a practical two-dimensional model for turbulent and mixed regimes in narrow annular displacement flows, such as are found during the primary cementing of oil and gas wells. Such mixed cross regimes, including those in which different regimes exist in the same annular cross section, are relatively common in primary cementing. The modelling approach considers scaling based on the disparity of length-scales, which allows a narrow-gap averaging approach to be effective. With respect to the momentum equations, the leading-order equations correspond to a turbulent shear flow in the direction of the modified pressure gradient. This leads to a nonlinear elliptic problem that is the natural extension of the laminar displacement model in Bittleston et al. (J Eng Math 43:229–253, 2002). The mass transport equations that model the miscible displacement are however quite different. To leading-order turbulence effectively mixes the fluids. Changes in concentrations within the annular gap arise due to the combined effects of advection with the mean flow, anisotropic Taylor dispersion (along the streamlines) and turbulent diffusivity. The diffusive and dispersive effects are modelled for fully turbulent and transitional flows following Maleki and Frigaard (J Non-Newt Fluid Mech 235:1–19, 2016). The model derived allows the investigation of different well geometries and inclinations, pumping sequences and fluid rheologies, all of which can have importance. A number of computed examples are presented with the aim of demonstrating the complexity of turbulent displacements.

Buoyancy effects on micro-annulus formation: Density stable displacement of Newtonian–Bingham fluids

Buoyant miscible displacement flow of a Bingham fluid by a Newtonian fluid along a vertical plane-channel is studied, in the high Péclet number regime. The displacing fluid is denser than the displaced fluid and the flow direction is density-stable (upwards). The flow is effectively governed by 4 dimensionless parameters: the Newtonian Bingham number (BN), the viscosity ratio (m), the Reynolds number (Re), and modified Froude number (Fr). This is a simple model for micro-annulus formation in the primary cementing of oil and gas wells. We show that the residual layer thickness is largely determined by two parameters: (BN/m, χ*/m), where χ*=2ReFr2. Residual wall layers may be either static or mobile, and mobile layers either evolve to become static or are washed from the channel at long times. We show that the different behaviours of the residual layers are linked to different characteristic behaviours of the displacement front, and we show how the latter behaviours can be predicted using a lubrication/thin-film approximation.

Effects of carbon dioxide in Portland cement: A relation between static sedimentation and carbonation

Two Portland cement slurries were intentionally formulated with characteristic and distinct behaviors. The slurries have in their composition conventional chemical additives that are frequently used in the cementing of oil wells and class G cement. One of the slurries have the capacity to keep the elements in suspension, producing a stable system (ST), while the other one produce particle’s sedimentation, promoting an unstable system (UN). Both slurries were carbonated for 30days in an autoclave with a CO2 saturate environment. The carbonated samples were characterized by static sedimentation test, acid-base indicator analysis and X-ray diffraction with Rietveld refinement. It was observed that the carbonation phenomenon occurs peculiarly when the cement slurry presents sedimentation of particles. So, a model for the sedimentation and carbonation behavior was proposed for the unstable slurry based on fluid mechanics. The study proposes that stability to sedimentation is a prerequisite considered with great discretion for the studies that aim to evaluate systems submitted to the attack of CO2. Failure to observe this prerequisite may result in inconsistent information that may lead to false positive or false negative results.

Evaluation of cement thixotropy for the cement of oil wells in areas with losses: Effect of plaster and dairy of high furnaces

Cementing of oil and gas wells can be a very delicate operation. Among the concerns of service companies, during this operation are the nature and conditions of the formations in well. This is the case of cementing operations in southern Algeria, specifically on the fields of In-Amen, where the formations in zones are naturally weak and highly permeable. In these areas, drilling fluids (muds and cements) pumped will be, completely or partially lost, what we call lost circulation. Thixotropic cements are useful to overcome circulation problems. They are characterized by a special rheological behavior, allowing it to plug zones when they are pumped. Our work aims to assess the thixotropy of cements perapred with two types of cement (class G Asland cement and CEM I 42.5 portland cement) with the plaster, using a viscometer with coaxial cylinder (couette type). Moreover, the effect of blast furnace slag (LHF) on the properties and thixotropic mixtures prepared was also studied. The results show that portland cement (available locally) can produce mixes with higher and more stable thixotropy than the class G cement (from importation), which is a practical and economical for cementing job operations in wells with loss zones. The results also show that the effect of LHF is positive, since in addition to his contribution to long term performances, especially the durability of hardened concrete, it improves the thixotropy of cement made of plaster.

Portland Cement for the Cementing of Oil Wells Developed with the Aid of the Rietveld Refinement Method

The use of the Rietveld refinement method has been highlightened as essential in the characterization of polycrystalline materials. With the aid of this method, combined with the application of the X-ray diffraction, it was possible to develop a type of cement that can temporarily substitute the Portland cement for Oil well. This cement was developed from the mixture of Portland cements commonly found in the market. The cements were passed through various sieves, then characterized by X-ray diffraction, being identified the main phases (C3A, C4AF, C3S and C2S) and quantified by the Rietveld refinement method. With the values obtained in the quantification of the phases, a new cement was made through the method of linear programming. From the results, it was possible to conclude that the developed cement presented a composition (levels of the main phases) that satisfies the requirements of NBR 9831, mainly in relation to the low levels of C3A.

Oil Well Cement Developed from Common Cement: Physical, Chemical and Mineral Characterization

This study aims to characterize a new type of cement, produced from the mixture of common Portland cements, which could be used as an option in the cementing of oil wells. To enable this study a linear programming method was used for the composition of the new cement, then, characterization tests were performed through particle size analysis by laser diffraction, chemical analysis by EDX, thermogravimetric analysis, X-ray diffraction, setting time, compressive strength. The results allowed the conclusion that the new formulated cement presented low C3A content, time setting superior to the Portland Cement for Oil Well, thermal stability up to 500 °C, low hydration kinetics and content of the main components coherent to the ABNT specifications.

Displacement flows in horizontal, narrow, eccentric annuli with a moving inner cylinder

We analyze the effects of rotation and axial motion of the inner cylinder of an eccentric annular duct during the displacement flow between two Newtonian fluids of differing density and viscosity. The annulus is assumed narrow and is oriented near the horizontal. The main application is the primary cementing of horizontal oil and gas wells, in which casing rotation and reciprocation is becoming common. In this application it is usual for the displacing fluid to have a larger viscosity than the displaced fluid. We show that steady traveling wave displacements may occur, as for the situation with stationary walls. For small buoyancy numbers and when the annulus is near to concentric, the interface is nearly flat and a perturbation solution can be found analytically. This solution shows that rotation reduces the extension of the interface in the axial direction and also results in an azimuthal phase shift of the steady shape away from a symmetrical profile. Numerical solution is used for larger buoyancy numbers. We see that the phase shift results in the positioning of heavy fluid over light fluid along segments of the interface. When the axial extension of the interface is sufficiently large, this leads to a local buoyancy-driven fingering instability, for which a simple predictive theory is advanced. Over longer times, the local fingering is replaced by steady propagation of a diffuse interfacial region that spreads slowly due to dispersion. Slow axial motion of the annulus walls on its own is apparently less interesting. There is no breaking of the symmetry of the interface and hence no instability. However, axial wall motion does generate secondary flows which may combine with those from cylinder rotation resulting in enhanced dispersive effects.