Experiments on Fluid Placement in a Confined Pipe: Fluid Mechanics Analysis for Plug and Abandonment Applications

2020 ◽  
Author(s):  
Soheil Akbari ◽  
Seyed Mohammad Taghavi
Keyword(s):  
Oil And Gas ◽  
Drilling Fluid ◽  
Heavy Fluid ◽  
Cement Slurry ◽  
Gas Wells ◽  
Inflow Velocity ◽  
Operation Conditions ◽  
Oil And Gas Wells ◽  
Cement Plug

Abstract Plug and abandonment (P&A) of oil and gas wells is an essential process to prevent the oil and gas reservoir fluids migration over time and possibly contaminating other formations and also fresh water resources. In order to plug and abandon a well, a high quality cement plug placement is required. One of the most common methods of cement plug placement is the dump bailing method. In this method, a fixed volume of cement is dumped using a bailer on a mechanical plug in the wellbore. The cement slurry occupies the wellbore and also the annular region outside the dump bailer. In the processes of cement slurry placement, an extensive range of Newtonian or non-Newtonian fluids is used to remove the in-situ fluid (drilling fluid or water) in the wellbore. Based on the large number of parameters such as the density and viscosity differences between the fluids, the geometry type (pipe, annulus, etc.), the operation conditions (velocity, geometry inclination, dumping height), various kinds of placement and mixing flows can occur, and different flow regimes (e.g. inertial, viscous) can develop. In this paper, we experimentally study the placement of a heavy fluid to replace an in-situ light fluid in an inclined closed-end pipe (representative of the dump bailing method). The two fluids are Newtonian and miscible, and they have the same viscosity. We investigate the effects of some of the flow parameters such as the dumping height, the pipe inclination, and the inflow velocity of the heavy fluid on the degree of mixing and the placement quality and efficiency. Our results show that the the most efficient displacement happens with the shortest dumping height and at lower inclination from vertical. Also, a high inflow velocity displaces the light fluid promptly with more mixing in comparison with a low inflow rate. The results can help us to develop strategies for improving the dump bailing method in the P&A of the oil and gas wells.

Analyzing the Fluid Mechanics of the Dump Bailing Method in the Plug and Abandonment of Oil and Gas Wells

2021 ◽  
Author(s):  
Soheil Akbari ◽  
Seyed Mohammad Taghavi
Keyword(s):  
Fluid Mechanics ◽  
Oil And Gas ◽  
Cement Slurry ◽  
Gas Wells ◽  
Two Fluids ◽  
Oil And Gas Wells ◽  
Fluid Properties ◽  
Flow Quality ◽  
Cement Plug

Abstract Plug and abandonment (P&A) of oil and gas wells is receiving an increased attention. The P&A operation is performed by placing a barrier, such as a cement plug to avoid reservoir fluids migration toward aquifers. To fulfill these requirements, the desired cement plug should be placed in the wellbore with minimum mixing with the in-situ fluid. A rigless way for placing cement slurry in the wellbore is through the dump bailing method, in which a relatively small amount of cement slurry is injected on a mechanical barrier inside the well to replace the in-situ wellbore fluids (mostly fresh water). The dynamics of the fluid placement is governed by several parameters, such as the flow and geometry parameters, and the fluid properties. In this study, we analyze the fluid mechanics of the dump bailing method, via experimentally investigating the effects of the viscosity ratio between the replacing and replaced fluids in the process. The viscosities of the fluids involved have significant effects on the mixing and placement flow quality. In our experiments, the fluid placement is carried out in a near-vertical closed-end pipe (i.e. representative of the well casing) to replace an in-situ light fluid. The two fluids are considered to be miscible, and they have a fixed density difference. Our results show that the most efficient placement happens with the injection of the higher viscous fluid. The outcomes of this study can be used for improving the cementing processes in the dump-bailing method of P&A operations.

Well Clean-Up Using a Combined Thermochemical/Chelating Agent Fluids

2019 ◽  
Vol 141 (10) ◽  
Author(s):  
Mohamed Mahmoud
Keyword(s):  
High Temperature ◽  
Filter Cake ◽  
Oil And Gas ◽  
Drilling Fluid ◽  
Chelating Agent ◽  
Drilling Fluids ◽  
Gas Wells ◽  
Oil And Gas Wells ◽  
Different Types ◽  
Cake Removal

The well clean-up process involves the removal of impermeable filter cake from the formation face. This process is essential to allow the formation fluids to flow from the reservoir to the wellbore. Different types of drilling fluids such as oil- and water-based drilling fluids are used to drill oil and gas wells. These drilling fluids are weighted with different weighting materials such as bentonite, calcium carbonate, and barite. The filter cake that forms on the formation face consists mainly of the drilling fluid weighting materials (around 90%), and the rest is other additives such as polymers or oil in the case of oil-base drilling fluids. The process of filter cake removal is very complicated because it involves more than one stage due to the compatibility issues of the fluids used to remove the filter cake. Different formulations were used to remove different types of filter cake, but the problem with these methods is the removal efficiency or the compatibility. In this paper, a new method was developed to remove different types of filter cakes and to clean-up oil and gas wells after drilling operations. Thermochemical fluids that consist of two inert salts when mixed together will generate very high pressure and high temperature in addition to hot water and hot nitrogen. These fluids are sodium nitrate and ammonium chloride. The filter cake was formed using barite and calcite water- and oil-based drilling fluids at high pressure and high temperature. The removal process started by injecting 500 ml of the two salts and left for different time periods from 6 to 24 h. The results of this study showed that the newly developed method of thermochemical removed the filter cake after 6 h with a removal efficiency of 89 wt% for the barite filter cake in the water-based drilling fluid. The mechanisms of removal using the combined solution of thermochemical fluid and ethylenediamine tetra-acetic acid (EDTA) chelating agent were explained by the generation of a strong pressure pulse that disturbed the filter cake and the generation of the high temperature that enhanced the barite dissolution and polymer degradation. This solution for filter cake removal works for reservoir temperatures greater than 100 °C.

scholarly journals Potential use of basidiomycota Trametes hirsuta MT-17.24 in biodegradation of polyanionic cellulose

2021 ◽  
Vol 11 (3) ◽  
pp. 472-480
Author(s):  
A. V. Zubchenko ◽  
E. Yu. Kozhevnikova ◽  
A. V. Barkov ◽  
Yu. A. Topolyuk ◽  
A. V. Shnyreva ◽  
...  
Keyword(s):  
Enzyme Preparation ◽  
Oil And Gas ◽  
Drilling Fluid ◽  
Schizophyllum Commune ◽  
Cellulase Activity ◽  
Drilling Fluids ◽  
Gas Wells ◽  
Trametes Hirsuta ◽  
Enzyme Preparations ◽  
Oil And Gas Wells

Abstract: Despite their efficiency, existing methods to dispose of drilling fluids used in the construction of oil and gas wells (chemical treatment of spent solutions, thermal method, thickening) are often expensive and unsustainable. Basidiomycota are natural xylotroph destructors that process lignocellulosic substrate – one of the most stable biopolymers in nature. Prospects for using enzyme preparations based on Basidiomycota as biodestructors of organic substances are evident due to the high efficiency and zero-waste production. The aim was to obtain an enzyme preparation based on the Trametes hirsute MT-17.24 Basidiomycota strain and evaluate its ability to biodegrade polyanionic cellulose, used as a viscosifier for drilling fluids in the construction and repair of oil and gas wells. Screening of cellulase activity of the following strains was carried out: Fomitopsis pinicola MT-5.21, Fomes fomentarius MT-4.05, Lactarius necator, Schizophyllum commune MT-33.01, Trametes versicolor It-1, Trametes hirsute MT-17.24, Trametes hirsuta MT-24.24. To obtain the enzyme preparation, the T. hirsuta MT-17.24 strain was selected, which demonstrated the highest coefficient of cellulase activity (10.9). A medium for solid-phase cultivation of this strain was selected. Enzymatic activity of the enzyme preparation was studied on a model drilling fluid. A 10-hour experiment showed that the use of a 1% enzyme preparation leads to a decrease in the plastic viscosity of the drilling fluid from 16 to 8 mPa·s. The research results demonstrate the efficiency of enzyme preparations based on Basidiomycota in the biodestruction of polyanionic cellulose.

scholarly journals Investigation of Non-Linear Rheological Characteristics of Barite-Free Drilling Fluids

Fluids ◽  
2021 ◽  
Vol 6 (9) ◽  
pp. 327
Author(s):  
Ekaterina Leusheva ◽  
Nataliia Brovkina ◽  
Valentin Morenov
Keyword(s):  
Oil And Gas ◽  
Drilling Fluid ◽  
Rheological Parameters ◽  
Drilling Fluids ◽  
Drilling Mud ◽  
Gas Wells ◽  
Oil And Gas Wells ◽  
Fluid Properties ◽  
Hydrolyzed Polyacrylamide ◽  
Drilling Muds

Drilling fluids play an important role in the construction of oil and gas wells. Furthermore, drilling of oil and gas wells at offshore fields is an even more complex task that requires application of specialized drilling muds, which are non-Newtonian and complex fluids. With regard to fluid properties, it is necessary to manage the equivalent circulation density because its high values can lead to fracture in the formation, loss of circulation and wellbore instability. Thus, rheology of the used drilling mud has a significant impact on the equivalent circulation density. The aim of the present research is to develop compositions of drilling muds with a low solids load based on salts of formate acid and improve their rheological parameters for wells with a narrow drilling fluid density range. Partially hydrolyzed polyacrylamide of different molecular weights was proposed as a replacement for hydrolized polyacrylamide. The experiment was conducted on a Fann rotary viscometer. The article presents experimentally obtained data of indicators such as plastic viscosity, yield point, nonlinearity index and consistency coefficient. Experimental data were analyzed by the method of approximation. Analysis is performed in order to determine the most suitable rheological model, which describes the investigated fluids’ flow with the least error.

Effect of Fluid Type and Multiphase Flow on Sand Production in Oil and Gas Wells

SPE Journal ◽  
2018 ◽  
Vol 24 (02) ◽  
pp. 733-743
Author(s):  
Haotian Wang ◽  
Deepen P. Gala ◽  
Mukul M. Sharma
Keyword(s):  
Fluid Flow ◽  
Oil And Gas ◽  
Rock Strength ◽  
Oil Wells ◽  
Darcy Flow ◽  
Sand Production ◽  
Gas Wells ◽  
Drag Forces ◽  
Oil And Gas Wells

Summary Controlled laboratory experiments and some field studies have shown that the onset of sand production in gas wells differs from that in oil wells. Results from a general 3D sand-production numerical model are presented to explain the differences in the onset of sanding and sand-production volume for different fluids and under different flow and in-situ stress conditions. The sand-production model accounts for multiphase-fluid flow and is fully coupled with an elasto-plastic geomechanical model. The sanding criterion considers both mechanical failure and sand erosion by fluid flow. Non-Darcy flow is implemented to account for the high flow rates. The drag forces on the sand grains are computed on the basis of the in-situ Reynolds number. Both the intact rock strength and the residual rock strength depend on water saturation. Water evaporation (drying) resulting from gas flow is modeled using phase equilibrium calculations. The onset of sand production is compared for different fluid types (oil and gas). Model results are shown to be consistent with experimental observations reported in the literature. For example, the onset of sanding is observed at higher compressive stresses for gas wells as compared with oil wells. The primary mechanism for this is for the first time shown to be sand strengthening induced by evaporation of water. This effect is not observed in oil wells. The sand-production rate when non-Darcy effects are considered is lower than for Darcy flow. The reason for this is the lower fluid velocity (for the same drawdown) and, consequently, smaller drag forces on the failed sand grains. The effect of water breakthrough and water cut on sand production is studied from both mechanical and erosion perspectives. The model is shown to be capable of accurately predicting the onset of sanding and sand production induced by multiphase- and compressible-fluid flows, helping us to predict sanding issues in both oil and gas wells.

Buoyant Miscible Jets in the Plug and Abandonment of Oil and Gas Wells

2021 ◽  
Author(s):  
Hossein Hassanzadeh ◽  
Ali Eslami ◽  
Seyed Mohammad Taghavi
Keyword(s):  
Oil And Gas ◽  
Injection Velocity ◽  
Target Area ◽  
Cleaning Process ◽  
Ambient Fluid ◽  
Gas Wells ◽  
Cleaning Efficiency ◽  
Buoyant Jets ◽  
Oil And Gas Wells ◽  
Cement Plug

Abstract The plug and abandonment (P&A) operation is the final stage in the life cycle of oil and gas wells. The aims of the P&A operation are to seal the well and permanently maintain the well-integrity similar to that of the original natural caprock. Using this approach, it is possible to isolate fluids movement between different strata, to prevent environmental disasters. Generally, the main steps in the P&A operation are (i) accessing the annulus section of the well, (ii) cleaning the defected area, and (iii) placing the cement plug barriers into the target area. To prepare the target area and avoid cement plug contamination, a cleaning process is required inside and outside the casing. The jet cleaning process is one of the effective methods for the cleaning step, in which a liquid of a higher density is usually injected into the target area to displace a lighter ambient fluid. During the jet cleaning process, several forces affect the cleaning efficiency, including inertial, viscous and buoyancy forces. In this work, we analyze a fundamental component of the jet cleaning process in the P&A operation, via experimentally studying the characteristics of a miscible positively buoyant jet. In our work, a heavy fluid is injected downwards into a large rectangular tank filled with a light ambient fluid. Due to the large dimensions of the experimental tank, the wall effects on the flow are neglected, i.e. we consider a free jet. We investigate some of the parameters affecting the behaviour of our positively buoyant jets, such as the injection velocity, the nozzle diameter, and the ratio between the viscosity of the jet fluid to that of the ambient fluid. In the parameter ranges of our interest, the jet flow exhibits certain critical flow features, such as the laminar length (i.e. the initial stable part of the jet where the injection fluid remains laminar and does not mix with the ambient fluid) and the spread angle (i.e. the area occupied by the jet). Our results show that both the laminar length and the spread angle decrease by increasing the injection velocity. In addition, increasing the viscosity ratio results in increasing the maximum laminar length and decreasing the spread angle. These results can help to better design an efficient cleaning in the P&A operation of oil and gas wells.

Effect of Nanocellulose in Cement Systems

2021 ◽  
Author(s):  
Animesh Kumar ◽  
Devesh Bhaisora ◽  
Mikhil Dange
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Oil And Gas ◽  
Aqueous Suspension ◽  
Weight Ratio ◽  
Cementitious Materials ◽  
Cement Slurry ◽  
Gas Wells ◽  
Oil And Gas Wells ◽  
Cement System

Abstract Cellulose, the one of the most abundant biomaterials available in nature, is a polymer with cellobiose as the smallest repeating unit, with a degree of polymerization that can go up to 1000 for wood cellulose. The strength-to-weight ratio of nanocellulose is eight times greater than steel (Patchiya Phanthong et al). Nanocellulose in suspension (NCS) at a varied concentration helps increase properties of cement without changing the density of the cement slurry. Being mindful of challenges in oil and gas wells, efforts were made to enhance cement properties using nanocellulose within conventional and water-extended cement systems. Samples of 15.8-ppg conventional and 12 ppg water-extended cements were prepared by varying the proportion of nanocellulose within an aqueous suspension. Rheology, sedimentation, compressive strength and mechanical properties were analyzed for a conventional 15.8-ppg cement system with varying NCS proportions of 0, 2, 4, and 5% by weight of cement (BWOC). Similar work was performed for a 12 ppg water-extended cement system by varying NCS differently in proportions of 0, 5, 10, and 20% BWOC. Two-inch cubes were set at 170°F for 24 hours for each sample. They were crushed using hydraulic crush compressive strength equipment, and the force used to break the sample was recorded. Compressive strength for this cement system was measured to be 2450, 3250, 3450, and 3875 psi, respectively, for samples with 0, 2, 4, and 5% BWOC concentrations of NCS. An increase in the strength of cement with an increase in NCS percentage was observed for the 15.8-ppg slurry design, which may be attributed to the size and shape of the NCS. However, similar study carried out with 12 ppg water extended slurries showed decrease in overall compressive strength. Nano-sized particles fill the pores within the sample, impacting structural network development. Additionally, cellulose, having a fiber-like structure, may provide inter-particulate reinforcement. Based on the results of the 15.8-ppg cement system and the high tensile strength of nanocellulose, it can be determined that NCS has a positive effect for increasing mechanical properties. By applying nanocellulose, a tailored cement system (dependable barrier) can be designed to minimize risk and maximize production from oil and gas wells. Nanocellulose is of increasing interest for a range of applications relevant to the fields of material science and biomedical engineering because of its renewable nature, anisotropic shape, excellent mechanical properties, good biocompatibility, tailorable surface chemistry, and interesting optical properties. Low-volume NCS additions can alter the structure of the cured cement system and increase its mechanical properties. This reinforcing mechanism may provide a new opportunity for achieving higher strength cementitious materials.

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