Pilot-Scale Experimental Study and Mathematical Modeling of Buoyant Settling of Immiscible Heavy Fluid in Mud To Stop Annular-Gas Migration Above Leaking Cement

SPE Journal ◽  
2017 ◽  
Vol 23 (01) ◽  
pp. 186-204
Author(s):  
Efecan Demirci ◽  
Andrew K. Wojtanowicz
Keyword(s):  
Pressure Change ◽  
Pilot Scale ◽  
Injection Rate ◽  
Gas Migration ◽  
Heavy Fluid ◽  
Process Measures ◽  
Gas Leakage ◽  
Two Fluids ◽  
High Dependency ◽  
Casing Pressure

Summary Annular casing pressure (ACP) is defined as the accumulated pressure on the casing head. If pressure returns after bleed-down, then the casing annulus is said to be showing sustained casing pressure (SCP). SCP is caused by late gas migration in the annular-fluid column above the top of leaking cement and may result in atmospheric emissions or underground blowouts. Removal of SCP is required in places where SCP is regulated, particularly before the well-plugging and abandonment operations. Annular-intervention methods for SCP removal, which are less expensive than the conventional downhole-intervention methods, typically involve injecting heavy fluid into the affected annulus that would displace the annular fluid (AF), balance the pressure at the top of cement, and stop the gas leakage. Previous studies stated that the use of immiscible combinations of two fluids is more effective for the purpose; however, inattentive applications may result in excessive use of heavy fluid. In this study, a 20-ft carbon-steel pilot-well annulus was manufactured and used for displacement experiments with various water-based drilling muds and heavy fluids with different properties. Pressure-change data were collected from four different levels of the annulus, and volumes of fluids going in and out of the annulus were measured. Experiments indicated the formation of a mixture zone that would build bottoms up and expand during ongoing displacement. The proposed pressure-buildup model suggests an exponential distribution of density of this zone, and shows its high dependency on fluids’ properties and injection rate. The mathematical models were also converted into dimensionless process measures and proposed for use in real-well applications. The study demonstrates the viability and recommends the correct application of the method.

Laboratory Visualization of Gravity Fluid Displacement in Well Annulus Affected by Sustained Casing Pressure

2015 ◽  
Author(s):  
Efecan Demirci ◽  
Andrew K. Wojtanowicz
Keyword(s):  
Injection Rate ◽  
Fluid Displacement ◽  
Two Fluids ◽  
Gas Leak ◽  
Displacement Experiments ◽  
Sustained Casing Pressure ◽  
Petroleum Wells ◽  
Casing Pressure ◽  
Well Cement ◽  
Synthetic Clay

Sustained Casing Pressure (SCP) in petroleum wells poses environmental risk and needs to be removed using either downhole intervention or annular intervention methods. The latter method involves displacing the annular fluid above the top of the gas-leaking well cement with a heavy fluid to increase the hydrostatic pressure and stop the gas leak. Past field applications of the method failed — most likely due to incompatibility of the two fluids. In this study, a see-through scaled-down hydraulic analog of the well’s annulus was designed and used for video-taped displacement experiments with clear synthetic-clay muds and heavy (kill) fluids. The results show that only immiscible hydrophobic kill fluids provide effective displacement. The study demonstrates importance of controlled injection of the kill fluid to set out efficient buoyant settling and prevent initial dispersion. A side- (versus top-) injection geometry and the injection rate data are analyzed to develop empirical correlation of maximum injection rate for a given properties of the two fluids.

scholarly journals Analytical and Experimental Investigation of the Critical Length in Casing–Liner Overlap

2019 ◽  
Vol 11 (23) ◽  
pp. 6861 ◽  
Author(s):  
Mustafa Al Ramadan ◽  
Saeed Salehi ◽  
Chinedum Ezeakacha ◽  
Catalin Teodoriu
Keyword(s):  
Critical Length ◽  
Fluid Migration ◽  
Test Duration ◽  
Gas Migration ◽  
Gas Leakage ◽  
Pressure Test ◽  
Seal Assembly ◽  
Casing Pressure ◽  
The Cost ◽  
Selection Of

Offshore drilling operations exhibit various difficulties attributed to shallow flows worldwide. One of the most common practices for drilling offshore wells is to use liners and liner hangers rather than using full casing strings. This reduces the cost of drilling operation. Liners and liner hangers are required to pass certain standards prior to their deployment in the field. This ensures their ability to withstand harsh downhole conditions and maintain the integrity of the well. A liner hanger contains an integrated seal assembly that acts as a barrier to prevent fluid migration. The cement that is placed within the casing–liner overlap is also considered a barrier, and it is critical that it maintains the integrity of the well by mitigating fluid migration to other formations and to the surface. The failure of this dual barrier (cement and seal assembly) system to seal the annular space can result in serious problems that might jeopardize a well’s integrity. Typically, in field applications, the length of a casing–liner overlap is chosen arbitrarily. In some cases, shorter overlaps (50 to 200 ft) are chosen because of the lower cost and easy identification of leaks during pressure tests. However, some loss of well control incidents (particularly the incident that motivated this study) have been linked to fluid leakages along the casing–liner overlap. This paper investigates the critical length of the casing–liner overlap by modeling gas leakage through the cement placed within the overlap using analytical and experimental approaches. Leakage scenarios were developed to mimic gas migration within the cement in the casing–liner overlap. The results showed that the longer the casing–liner overlap, the higher the leakage time. The results also showed that the current casing pressure test duration of 30 min may not be adequate to verify the integrity of the cement within the overlap. Based on the results and analyses, it is recommended to increase the pressure test duration to 90 min. In addition, the results suggest that the length of the casing–liner overlap should not be less than 300 ft to maintain the integrity of the well in the case of gas influx. Further details are highlighted in the results section. In practice, the current rationale behind the selection of a casing–liner overlap length is not sustainable. Thus, the major advantage of this study is that with field data, it provides both scientific and research-based evidence that can be used to inform the decision behind the selection of the casing–liner overlap length, especially in gas migration-prone zones.

scholarly journals A Prediction Model for Sustained Casing Pressure under the Effect of Gas Migration Variety

2019 ◽  
Vol 2019 ◽  
pp. 1-9
Author(s):  
Fuping Feng ◽  
Ziyuan Cong ◽  
Wuyi Shan ◽  
Chaoyang Hu ◽  
Maosen Yan ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Prediction Model ◽  
Recovery Time ◽  
Oil And Gas ◽  
Pressure Recovery ◽  
Flow State ◽  
Gas Migration ◽  
Gas Leakage ◽  
Sustained Casing Pressure ◽  
Casing Pressure

Sustained casing pressure (SCP) is a challenge in the well integrity management in oil and gas fields around the world. The flow state of leaked gas will change when migrated up annulus protective fluid. To show the influence of gas migration on casing pressure recovery, a prediction model of SCP based on Reynolds number of bubbles was established. The casing pressure prediction of typical wells and the sensitivity analysis of casing pressure are performed. The results show that the casing pressure recovery time decreases with the increase of cement permeability. However, larger cement permeability has little effect on the casing pressure after stabilization. Increasing the height of annulus protective fluid reduces the stable casing pressure value and shortens the casing pressure recovery time. Compared with the existing models, the results show that the time of casing pressure recovery will be shortened by the change of gas migration, and the effect of bubbles Re < 1 on SCP will be greater. The new model can be used to detect and treat the SCP problem caused by small Reynolds number gas leakage.

scholarly journals ESTIMATION OF THE MAIN GAS PIPELINE OPERATION UNDER EMERGENCY CONDITIONS OF GAS LEAKAGE

2019 ◽  
pp. 122-131
Author(s):  
V. T. Bolonny
Keyword(s):  
Linear Part ◽  
Pressure Change ◽  
Gas Pipeline ◽  
Oscillatory Process ◽  
Gas Filtration ◽  
System Failures ◽  
Filtration Resistance ◽  
Gas Leakage ◽  
Emergency Situations ◽  
Time Period

The characteristics of the gas transportation system of Ukraine are presented, the emergency risks of domestic gas transportation pipeline sys­tems are established. The analysis of the accident rate of gas pipeline trans­port in Ukraine and Russia was carried out. Presented technique of deter­mining the emergency pressure in the pipeline, depending on the amount of gas losses from pipeline at the point of its leakage provides an opportunity to determine the volume of gas losses from the pipeline and to evaluate the environmental risks due to emergency situations of gas pipeline transport. This technique makes it possible to calculate the pressure at each point of pipeline under nonstationary conditions caused by changes in pressure at the beginning and at the end of the sector and the emergence of concentrated gas leakage. Based on the results of calculations, a graph of pressure change of the oscillatory process in the gas pipeline caused by jump of pressures at the beginning and at the end of the sector, and the presence of probable lea­kages at the determined point of the trace was constructed. The linear part of the main gas pipelines is the most dangerous object, as all emergency sit­uations are associated with emergency processes of different intensity in the form of gas leakage into the environment and in fact are dangerous when system failures appear. The process and the time period for the formation of the gas pollution zone depend on the amount of gas leakage, its intensity and depth of the gas pipeline. The filtration resistance of the soil as a porous medium, in particular its permeability, have a significant effect on the amount of gas leakage through corrosive orifice. As a result, there is a correlation between the amount of gas losses associated with the leakage, and the laws of its filtra­tion in the surrounding soil. As a result, the effect of gas filtration process in the soil in the event of leakage from pipelines has been investigated. The graphic dependence of change in pressure of the filtration resistance of the medium and the time-changing leakage which are designed for different soil characteristics is obtained.

Vertical gas migration associated with coal seam gas production

2016 ◽  
Vol 56 (2) ◽  
pp. 602
Author(s):  
Ludovic Ricard ◽  
Julian Strand
Keyword(s):  
Coal Seam ◽  
Risk Evaluation ◽  
Critical Role ◽  
Gas Production ◽  
Mitigation Strategies ◽  
Gas Migration ◽  
Coal Seam Gas ◽  
Gas Reservoirs ◽  
Gas Leakage ◽  
Migration Pathways

Gas migration outside coal seam gas reservoirs has been identified as a risk associated with CSG production. While such an event has not been reported or scientifically associated with CSG production, understanding the physical mechanism of the vertical migration in the overburden involved should gas leakage occur would improve mitigation strategies and risk evaluation. In this extended abstract, a series of key modelling scenarios of gas migration above the reservoir are developed. Interpretation of the scenarios highlights that: the seal/leakage nature of the overburden strongly impacts gas migration and volume of gas leaked; when leakage does occur, the leaked volume represents a very small portion of the original gas in place and volume of gas produced; the connectivity of the overburden plays a critical role on the gas migration pathways and volume of gas leaked; and, residual gas saturation, and relative permeability hysteresis provide means to trap the mobile gas, significantly reducing the volume of gas leaked reaching shallower formations.

Risk and Remediation of Irreducible Casing Pressure at Petroleum Wells

2014 ◽  
pp. 155-180 ◽  
Author(s):  
Andrew K. Wojtanowicz
Keyword(s):  
Oil Well ◽  
Gas Migration ◽  
Excessive Pressure ◽  
Wet Gas ◽  
Regulatory Approach ◽  
Sustained Casing Pressure ◽  
Small Cracks ◽  
Petroleum Wells ◽  
Casing Pressure ◽  
Well Cement

Oil well cement problems such as small cracks or channels may result in gas migration and lead to irreducible pressure at the casing head. Irreducible casing pressure also termed, Sustained Casing Pressure (SCP) is hazardous for a safe operation and the affected wells cannot be terminated without remedial operations. It is believed that even very small leaks might lead to continuous emissions of gas to the atmosphere. In the chapter, the author describes physical mechanisms of irreducible casing pressure and qualifies the associated risk by showing statistical data from the Gulf of Mexico and discussing the regulatory approach. This chapter also introduces a new approach to evaluate risk of casing pressure by computing a probable rate of atmospheric emissions from wells with failed casing heads resulting from excessive pressure. Also presented is a new method for assessing potential for self-plugging of such wells flowing wet gas as the gas migration channels could be plugged off by the condensate.

Biodesulfurization of a Coarse-Grained High Sulfur Coal in a Full-Scale Packed-Bed Bioreactor

2017 ◽  
Vol 262 ◽  
pp. 207-210 ◽  
Author(s):  
Ahmad Doodkanlou Milan ◽  
Ali Ahmadi ◽  
Seyed Mohammad Raouf Hosseini
Keyword(s):  
Sulfur Removal ◽  
Packed Bed ◽  
Pilot Scale ◽  
Injection Rate ◽  
Aeration Rate ◽  
Coarse Grained ◽  
Solution Ph ◽  
Packed Bed Bioreactor ◽  
Stirred Tank Reactors ◽  
Gypsum Precipitation

Biodesulfurization of a high-sulfur and medium-ash coal product was carried out in a 5-m tall packed bed bioreactor using a mixed culture of iron- and sulfur- oxidizing microorganisms. The feed coal (4 tones) was obtained from a heavy media cyclone product from Takht-Zeitoon coal mine (Tabas, Iran) with a density of -1.4 g/cm3 and a grain size of 0.5-25 mm, having the ash and sulfur contents of 14.92% and 2.46%, respectively. The pilot scale process was performed in a semi-continuous mode with a solution injection rate of 2.5-4.5 lit/min/m2, aeration rate of 4-12 m3/h/m2 and solution pH of 1.7-2, over a period of 190 days. Iron and sulfate ions were controlled during the process in two 1500-L stirred tank reactors by goethite and gypsum precipitation processes, respectively. The column biodesphurization in a period of 170 days was followed by a washing step with HCl to remove sulfate precipitates. Results showed that the total sulfur and ash contents reached to 1.69% and 11.04%, respectively, which were corresponded to 31% sulfur removal and 26% ash removal. It was indicated that biodesulfurization has a good industrial potential to treat coarse-grained high sulfur coals.

scholarly journals Investigating the Impact of Aquifer Parameters on Carbon Dioxide Dissolution in Saline Aquifers

2018 ◽  
Author(s):  
Mohsen Abbaszadeh ◽  
Seyed Shariatipour
Keyword(s):  
Carbon Dioxide ◽  
Pilot Scale ◽  
Vital Role ◽  
Injection Rate ◽  
Sensitivity Analyses ◽  
Absolute Permeability ◽  
Co2 Injection ◽  
Long Term Storage ◽  
Well Location ◽  
The Impact

CO2 injection into geological formations is considered one way of mitigating the increasing levels of carbon dioxide concentrations in the atmosphere and its effect on and global warming. In regard to sequestering carbon underground, different countries have conducted projects at commercial scale or pilot scale and some have plans to develop potential formations for carbon dioxide storage. In this study, pure CO2 injection is examined on a model with the properties of bunter sandstone and then sensitivity analyses were conducted for some of the important parameters. The results of this study show that the extent to which CO2 has been convected in the porous media in the reservoir plays a vital role in improving the CO2 dissolution in brine and safety of its long term storage. We conclude that heterogeneity plays a crucial role on the saturation distribution and can increase or decrease the amount of dissolved CO2 in water. Furthermore, the value of absolute permeability controls the effect of the Kv/Kh ratio on the CO2 dissolution in brine. In other words, as the value of vertical and horizontal permeability decreases (i.e. tight reservoirs) the impact of Kv/Kh ratio on the dissolved CO2 in brine becomes more prominent. Additionally, reservoir engineering parameters, such as well location, injection rate and scenarios, also have a high impact on the amount of dissolved CO2.

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