Gas Drilling Operations Research Articles

Oil Based Drilling Fluid Waste: An Overview on Environmentally Persistent Pollutants

Operational discharges of spent drilling fluid, produced water, and accumulated drill cuttings from oil and gas industry are a continuous point source of environmental pollution. To meet the strict environmental standard for waste disposal, oil and gas industry is facing a numerous challenges in technological development to ensure a clean and safe environment. Oil and gas industry generates a large amount of spent drilling fluid, produced water, and drill cuttings, which are very different in every drilling operation in terms of composition and characterisation. This review article highlights the knowledge gap in identifying the different sources of waste streams in combined drilling waste. This paper also emphasises how different chemicals turn into environmentally significant pollutants after serving great performance in oil and gas drilling operations. For instance, oil based drilling fluid performs excellent in deeper drilling and drilling in the harsh geological conditions, but ended with (produces) a significant amount of persistent toxic pollutants in the environment. This review paper provides an overview on the basic concepts of drilling fluids and their functions, sources and characterisation of drilling wastes, and highlights some environmentally significant elements including different minerals present in drilling waste stream.

Geometric optimisation of thermo-electric coolers using simulated annealing

The field of thermo-electric coolers (TEC) has grown drastically in recent years. In an extreme environment such as thermal energy and gas drilling operations, TEC is an effective cooling mechanism for instruments. Nevertheless, limitations such as the relatively low energy conversion efficiency and ability to dissipate only a limited amount of heat flux may seriously damage the lifetime and performance of the instrument. Many researches were conducted to expand the efficiency of TEC. The material parameters are the most significant, but they are restricted by currently available materials and module fabricating technologies. Therefore, the main objective of finding the optimal TEC design is to define a set of design parameters. In this paper, technical issues of TEC were discussed. After that, a new method of optimising the dimension of TEC using simulated annealing (SA), to maximise the cooling rate was proposed. Equality constraint and inequality constraint were taken into consideration. This work reve...

Utilization of Shredded Waste Car Tyres as a Fracture Seal Material (FSM) in Oil and Gas Drilling Operations

The drilling operation cost represents 25% of the total oilfield exploitation cost. Drilling fluids represent 15 to 18% of the total cost of well petroleum drilling operations. The main drilling fluids problem is the loss into fractures and vugs. Mitigation of severe lost circulation is a main challenge while drilling in fractured formations where conventional lost circulation materials (LCM) will not cure these losses. Therefore, specialized fracture seal material (FSM) is required when drilling fractured formations. In this study, a promising FSM made from shredded waste car tyres was tested at laboratory for its ability to seal artificially fractured cores under High Temperature High Pressure (HT-HP) conditions similar to wellbore conditions. For this purpose, the conventional 500 ml HT-HP filtration cell was modified to accommodate a fractured core plug of length and diameter equal to 38.1 mm (1.5 inches) instead of the ceramic disc. Moreover, the cell outlet channel located below the fractured plug was increased from 1.0 mm diameter to 5.0 mm to easily allow the passage of the FSM in none effective fracture seal tests. Using the modified HT-HP filtration cell shredded waste car tyres proved its ability to perfectly seal the artificially made fracture in the test core samples at overbalance pressures up to 900 psi and temperatures up to 80°C. The optimum mud composition was fresh water, 7% by weight bentonite, 7% shredded waste car tyres (a mixture ranging between 2.3 mm and less than 0.45 mm granule sizes) in weight bases. In addition to its great ability to seal fractured formation, the shredded waste car tyres material is cheap and locally available in commercial quantities. Additionally, the utilization of waste car tyres in drilling operations and other industrial applications can protect the environment from many hazards.

Time Optimizing near the Pay Zone

Well control techniques are used in oil and gas drilling operations to control bottom hole pressure and avoid any fluid influx from formation to the well. These techniques are highly important near the pay zone in term of time. Controlling formation fluid pressure and thereby the formations behavior in a predictable fashion will help toward more optimized environmental friendly drilling operation. Time consumed to control the formation fluid pressure will range between few hours to many days. This paper discusses hydrostatic pressure distribution and changes near the pay zone for one oil blocks in Kurdistan, in the northern part of Iraq. Obtaining homogeneous increase in some drilling fluid properties will help the engineer to better interpret sampling of the lithological columns and reduce potential hole problems and operation time.

Thermo-sensitive polymer nanospheres as a smart plugging agent for shale gas drilling operations

Emulsifier-free poly(methyl methacrylate–styrene) [P(MMA–St)] nanospheres with an average particle size of 100 nm were synthesized in an isopropyl alcohol–water medium by a solvothermal method. Then, through radical graft copolymerization of thermo-sensitive monomer N-isopropylacrylamide (NIPAm) and hydrophilic monomer acrylic acid (AA) onto the surface of P(MMA–St) nanospheres at 80 °C, a series of thermo-sensitive polymer nanospheres, named SD-SEAL with different lower critical solution temperatures (LCST), were prepared by adjusting the mole ratio of NIPAm to AA. The products were characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, thermogravimetric analysis, particle size distribution, and specific surface area analysis. The temperature-sensitive behavior was studied by light transmittance tests, while the sealing performance was investigated by pressure transmission tests with Lungmachi Formation shales. The experimental results showed that the synthesized nanoparticles are sensitive to temperature and had apparent LCST values which increased with an increase in hydrophilic monomer AA. When the temperature was higher than its LCST value, SD-SEAL played a dual role of physical plugging and chemical inhibition, slowed down pressure transmission, and reduced shale permeability remarkably. The plugged layer of shale was changed to being hydrophobic, which greatly improved the shale stability

Research advances and debates on tubular mechanics in oil and gas wells

Tubular strings in oil and gas wells are the backbone and central nervous system of oil and gas drilling and production operations. Tubular mechanics in oil and gas wells is the most important applied fundamental science in petroleum and gas engineering. This paper first introduces monographs on tubular mechanics in oil and gas wells, as well as scholars engaged in investigating this field. Then the methods used in this research are explored, and basic concepts are clarified. The paper then focuses on research progress and debates about the fundamental principles of tubular mechanics in oil and gas wells, the motion states of tubular strings in oil and gas wells, the fundamental equations for dynamic analysis of the rod and pipe string in oil and gas wells, the stability of the rod and pipe string in oil and gas wells, the steady-state tension and torque in the rod and pipe strings in oil and gas wells, three-dimensional mechanical analysis of the bottom hole assembly, the drill string dynamics, casing string mechanical analysis, testing string mechanical analysis, fracturing/water injection/steam injection tubing string mechanical analysis, diagnosis and parameter optimization of the sucker rod pump system as well as energy savings, vibration of the gas production tubing string, impact vibration of the string, expansion screen pipe/casing mechanical analysis, riser string and deepwater pipeline mechanical analysis, vibration wave signal transmission in the string, wear and corrosion as well as erosion of the string, and residual strength and fatigue strength forecasts, connections mechanical analysis, strength design and verification of the string. In the end, the paper discusses key future research directions.

Effect of Yield Power Law Fluid Rheological Properties on Cuttings Transport in Eccentric Horizontal Narrow Annulus

Narrow annular drilling such as casing-while-drilling technique is gaining popularity due to its ability to mitigate nonproductive time during oil and gas drilling operations. However, very little is known about the flow dynamics in narrow annular drilling. In this study, the Eulerian-Eulerian two-fluid model was used to examine the influence of Yield Power Law fluid rheological properties on cuttings transport in eccentric horizontal narrow annulus. The flow was assumed as fully developed, laminar, and transient state. The present simulation model was validated against experimental data, where a mean percent error of −1.2% was recorded. Results revealed an increase in the radial distribution of cuttings transport velocity in the wide annular region as the consistency index, K, and the flow behavior index, n, increase. Nonetheless, increasing the yield stress, τo, had insignificant effect on the cuttings transport velocity. Three-dimensional profiles showed how cuttings preferred to travel in less resistant flow area, whereas cuttings concentration builds up in the narrow annular region. Furthermore, annular frictional pressure losses also increased as K, n, and τo increased. This study serves as a guide to properly optimize drilling fluid rheological properties for efficient cuttings transport and equivalent circulating density (ECD) management in narrow annular drilling.

Design optimization of a prescribed vibration system using conjoint value analysis

This article details a novel design optimization strategy for a prescribed vibration system (PVS) used to mechanically filter solids from fluids in oil and gas drilling operations. A dynamic model of the PVS is developed, and the effects of disturbance torques are detailed. This model is used to predict the effects of design parameters on system performance and efficiency, as quantified by system attributes. Conjoint value analysis, a statistical technique commonly used in marketing science, is utilized to incorporate designer preferences. This approach effectively quantifies and optimizes preference-based trade-offs in the design process. The effects of designer preferences on system performance and efficiency are simulated. This novel optimization strategy yields improvements in all system attributes across all simulated vibration profiles, and is applicable to other industrial electromechanical systems.

Formulation and Environmental Impact Evaluation of Walnut and Soya Bean Oil Based Drilling Fluid

One of the oil and gas hazard that associated with drilling operation is oil based drilling fluid and its associated cutting disposition. It is highly imperative for policy maker to propagate the use of environmental friendly oil based mud for drilling operation. This paper formulated environmentally friendly oil based mud (using walnut and soya bean plant oil) that can carry out the same function as convectional oil based drilling fluid and equally meeting up with the HSE (Health, safety and environment) standard. Mud laboratory tests were carried out at standard condition on plant oil samples so as to ascertain the rheological properties of the drilling fluid formulations. The synthetic oil based was obtained from drilling company in Nigeria and was used as control experiment. At the end of the experiment, the properties of the walnut and soya beans based mud wascompared with industry oil based mud (synthetic oil based mud). All the results were shown to be similar to that of commercial synthetic oil based drilling mud which was gotten from the industry.From the results it can be seen that walnut and soya beans based mud actually gives a less toxic,better rheological properties, requires less waste disposal costs, hence making them more economically and technically viable for oil and gas drilling operation.

Developing a simple-to-use predictive model for prediction of hydrate formation temperature

ABSTRACTHydrate formation may be a common occurrence during oil and gas drilling and production operation when temperature of these solid crystalline compounds that formed in the presence of free water decreases at elevated pressure. Also, they have often been found responsible for operating difficulties at wellheads, pipelines and other processing equipment. Nowadays, because of the importance of predicting hydrate formation condition, different accurate methods have been used. Besides the experiential correlations that are common for predicting, the developments in the field of modelling led to the use of different methods in a thermodynamic way. In fact, because of the risk of experimental uncertainties and to remove the need for intricate analytic equations and empirical correlations, the computational intelligence model, which result in the lowest error and based on experimental data, is strongly proposed, in attempts to solve complex industrial problems. In this article, in order to predict gas hydrate formation condition, two smart techniques are established based on feed-forward neural network (artificial neural network (ANN)) which is optimised by imperialist competitive algorithm (ICA). The ICA-ANN model is conducted utilising the empirical data released in the literature and finally the performance of ICA-ANN model is compared with the conventional ANN model. Furthermore, they have been compared with an accurate thermodynamic model at different operating conditions. The outcomes, contrary to expectations, establish that the ICA-ANN model has poor performance when compared with the ANN.

Techbits: SPE Effluent Discharge Management Workshop Addresses Standards and Regulations

Techbits The SPE Trinidad and Tobago Section recently hosted an Applied Technology Workshop (ATW) on oil and gas effluent discharge management in Port of Spain, Trinidad and Tobago. The event brought together petroleum and petrochemical industry professionals involved in generating effluent discharges to the receiving environment, regulators, and those involved in the design, construction, operation, and maintenance of treatment systems for effluent discharge. The goals of the workshop were to Explore regional and international legislation as applied to effluent discharge in the oil and gas industry and compare with the local regulatory framework in Trinidad and Tobago. Define the compliance issues of water pollution rules in Trinidad and Tobago specific to the oil and gas industry. Obtain the industry best practice for effluent treatment and disposal with emphasis on large oil and gas drilling and production operations both onshore and offshore. Explore the available technology and its applicability to achieve compliance. There was a consensus that urgent collaborative action is needed among all stakeholders. The path forward received endorsement from the country’s regulators (the Ministry of Energy and Energy Affairs [MEEA] and the Environmental Management Authority [EMA]), operators, and service providers. The areas of focus in the workshop included legislative reform, use of applicable technology, and availability of resources. Legislative Reform Participants discussed the Trinidad and Tobago legislation pertaining to effluent discharges. There were also presentations on experiences setting effluent discharge standards in the North Sea using the Convention for the Protection of the Marine Environment of the Northeast Atlantic or OSPAR Convention, for possible use as a framework. The topics of discussion about legislative reform centered on the following: Are our current water pollution rules relevant and appropriately framed in the current environment? The consensus was that there is an opportunity for the review of the current Water Pollution Rules created in 2001 and amended in 2006. For example, there is the need for ambient water-quality standards coupled with discharge standards. Current discharge standards were deemed to be stringent by some presenters compared with other jurisdictions such as OSPAR. OSPAR is using a holistic or risk-based approach in regulating effluent by the use of mixing zones and impact-based ambient water-quality standards vs. technology-based discharge parameters. To develop new ambient water-quality standards, a baseline study must be conducted on the receiving environment of Trinidad and Tobago.

Energy requirements of the switchable polarity solvent forward osmosis (SPS-FO) water purification process

A model was developed to estimate the process energy requirements of a switchable polarity solvent forward osmosis (SPS FO) system for water purification from aqueous NaCl feed solution concentrations ranging from 0.5 to 4.0molal at an operational scale of 480m3/day (feed stream). The model indicates recovering approximately 90% of the water from a feed solution with NaCl concentration similar to seawater using SPS FO would have total equivalent energy requirements between 2.4 and 4.3kWh per m3 of purified water product. The process is predicted to be competitive with current costs for disposal/treatment of produced water from oil and gas drilling operations. Once scaled up the SPS FO process may be a thermally driven desalination process that can compete with the cost of seawater reverse osmosis.

Microwave remediation of oil well drill cuttings

Abstract Some types of drilling fluids commonly used in oil and gas drilling operations are highly toxic synthetic fluids with low biodegradability. These fluids contaminate drill cuttings, which must undergo decontamination before disposal. Microwave drying has been investigated as a remediation technique for drill cuttings. This work investigates the influence of the following variables and parameters on the microwave drying process: heterogeneous drying, initial drilling fluid content in the drill cuttings, mechanical stirring of the bed, and type of synthetic drilling fluid. The results indicate that temperature gradients within the cavity, intrusive effect of metals and the container edges influenced the heterogeneity of the process. An increase in initial drilling fluid content decreased the drying efficiency. Mechanical stirring of the bed increased the drying efficiency by up to 17%. The type of synthetic oil base in the drilling fluid did not significantly affect the drying kinetics.

Geometric Optimization of Thermo-electric Coolers Using Simulated Annealing

The field of thermo-electric coolers (TECs) has grown drastically in recent years. In an extreme environment as thermal energy and gas drilling operations, TEC is an effective cooling mechanism for instrument. However, limitations such as the relatively low energy conversion efficiency and ability to dissipate only a limited amount of heat flux may seriously damage the lifetime and performance of the instrument. Until now, many researches were conducted to expand the efficiency of TECs. The material parameters are the most significant, but they are restricted by currently available materials and module fabricating technologies. Therefore, the main objective of finding the optimal TECs design is to define a set of design parameters. In this paper, a new method of optimizing the dimension of TECs using simulated annealing (SA), to maximize the rate of refrigeration (ROR) was proposed. Equality constraint and inequality constraint were taken into consideration. This work reveals that SA shows better performance than Cheng's work.

Cuttings-liquid frictional pressure loss model for horizontal narrow annular flow with rotating drillpipe

During oil and gas drilling operations, frictional pressure loss is experienced as the drilling fluid transports the drilled cuttings from the bottom-hole, through the annulus, to the surface. Estimation of these pressure losses is critical when designing the drilling hydraulic program. Two-phase frictional pressure loss in the annulus is very difficult to predict, and even more complex when there is drillpipe rotation. Accurate prediction will ensure that the correct equivalent circulating density (ECD) is applied in the wellbore to prevent formation fracture, especially in formations with narrow window between the pore pressure and fracture gradient. Few researchers have attempted to propose cuttings-liquid frictional pressure loss models, nevertheless, these models fail when they are applied to narrow wellbores such as in casing- while-drilling and slimhole applications. This study proposes improved cuttings-liquid frictional pressure loss models for narrow horizontal annuli with drillpipe rotation using Dimensional Analysis. Both Newtonian and non-Newtonian fluids were considered. The proposed model constants were fitted by generated data from a full-scale simulation study using ANSYS-CFX. The models showed improvement over existing cuttings-liquid pressure loss correlations in literature.

The shale gas revolution from the viewpoint of a former industry insider.

This is an interview conducted with an oil and gas worker who was employed in the industry from 1993 to 2012. He requested that his name not be used. From 2008 to 2012, he drilled wells for a major operator in Bradford County, Pennsylvania. Bradford County is the center of the Marcellus shale gas boom in Northeastern Pennsylvania. In 2012, he formed a consulting business to assist clients who need information on the details of gas and oil drilling operations. In this interview, the worker describes the benefits and difficulties of the hard work involved in drilling unconventional gas wells in Pennsylvania. In particular, he outlines the safety procedures that were in place and how they sometimes failed, leading to workplace injuries. He provides a compelling view of the trade-offs between the economic opportunities of working on a rig and the dangers and stresses of working long hours under hazardous conditions.

Modified Yield Power‐Law fluid flow in narrow annuli with inner rotating pipe

AbstractA proposed viscosity model for Yield Power‐Law fluid by Souza Mendes and Dutra (SMD), devoid of discontinuities at vanishing shear rate, is adopted in a 3D CFD simulation study. Radial distributions of axial, tangential, and coupled components of velocities are measured along concentric and eccentric narrow annuli. The flow is assumed to be fully‐developed, laminar, and steady state. Several parameters such as diameter ratios, eccentricities, and inner pipe angular speeds were varied to analyze their influence on the flow distributions and annular pressure losses. The simulated results of radial distributions of axial and tangential velocities show good agreement with experimental data and analytic solutions from previous studies. Annular flow instabilities in the form of Taylor vortices in the flow fields are briefly discussed. This study shows how reliable CFD simulations can replicate the actual, yet complex, oil and gas drilling operations.

Popular epidemiology and "fracking": citizens' concerns regarding the economic, environmental, health and social impacts of unconventional natural gas drilling operations.

Pennsylvania sits atop the Marcellus Shale, a reservoir of natural gas that was untapped until the 2004 introduction of unconventional natural gas drilling operations (UNGDO) in the state. Colloquially known as fracking, UNGDO is a controversial process that employs large volumes of water to fracture the shale and capture gas; it has become a multi-billion dollar industry in Pennsylvania. We analyzed letters to the editor of the most widely circulated local newspaper in the most heavily drilled county in Pennsylvania (Bradford County) in order to characterize residents' concerns and their involvement in popular epidemiology--the process by which citizens investigate risks associated with a perceived environmental threat. We reviewed 215 letters to the editor that referenced natural gas operations and were published by The Daily Review between January 1, 2008 and June 8, 2013. We used NVivo 10 to code and analyze letters and identify major themes. Nvivo is qualitative data analysis software (http://www.qsrinternational.com/products_nvivo.aspx) that allows researchers to code and analyze "unstructured" data, including text files of any type (e.g., interview transcripts, news articles, letters, archival materials) as well as photographs and videos. Nvivo can be used to classify, sort, query, comment on, and share data across a research group. Letters demonstrated citizen engagement in beginning and intermediate stages of lay epidemiology, as well as discord and stress regarding four main issues: socio-economic impacts, perceived threats to water, population growth and implications, and changes to the rural landscape. Residents called for stronger scientific evidence and a balance of economic development and health and environmental protections. Citizens' distress regarding UNGDO appeared to be exacerbated by a dearth of information to guide economic growth and health, environmental, and social concerns. This analysis proposes locally informed questions to guide future surveillance and research.

Leakage detection of Marcellus Shale natural gas at an Upper Devonian gas monitoring well: a 3-d numerical modeling approach.

Potential natural gas leakage into shallow, overlying formations and aquifers from Marcellus Shale gas drilling operations is a public concern. However, before natural gas could reach underground sources of drinking water (USDW), it must pass through several geologic formations. Tracer and pressure monitoring in formations overlying the Marcellus could help detect natural gas leakage at hydraulic fracturing sites before it reaches USDW. In this study, a numerical simulation code (TOUGH 2) was used to investigate the potential for detecting leaking natural gas in such an overlying geologic formation. The modeled zone was based on a gas field in Greene County, Pennsylvania, undergoing production activities. The model assumed, hypothetically, that methane (CH4), the primary component of natural gas, with some tracer, was leaking around an existing well between the Marcellus Shale and the shallower and lower-pressure Bradford Formation. The leaky well was located 170 m away from a monitoring well, in the Bradford Formation. A simulation study was performed to determine how quickly the tracer monitoring could detect a leak of a known size. Using some typical parameters for the Bradford Formation, model results showed that a detectable tracer volume fraction of 2.0 × 10(-15) would be noted at the monitoring well in 9.8 years. The most rapid detection of tracer for the leak rates simulated was 81 days, but this scenario required that the leakage release point was at the same depth as the perforation zone of the monitoring well and the zones above and below the perforation zone had low permeability, which created a preferred tracer migration pathway along the perforation zone. Sensitivity analysis indicated that the time needed to detect CH4 leakage at the monitoring well was very sensitive to changes in the thickness of the high-permeability zone, CH4 leaking rate, and production rate of the monitoring well.

Using discriminant analysis to determine sources of salinity in shallow groundwater prior to hydraulic fracturing.

High-volume hydraulic fracturing (HVHF) gas-drilling operations in the Marcellus Play have raised environmental concerns, including the risk of groundwater contamination. Fingerprinting water impacted by gas-drilling operations is not trivial given other potential sources of contamination. We present a multivariate statistical modeling framework for developing a quantitative, geochemical fingerprinting tool to distinguish sources of high salinity in shallow groundwater. The model was developed using new geochemical data for 204 wells in New York State (NYS), which has a HVHF moratorium and published data for additional wells in NYS and several salinity sources (Appalachian Basin brines, road salt, septic effluent, and animal waste). The model incorporates a stochastic simulation to predict the geochemistry of high salinity (>20 mg/L Cl) groundwater impacted by different salinity sources and then employs linear discriminant analysis to classify samples from different populations. Model results indicate Appalachian Basin brines are the primary source of salinity in 35% of sampled NYS groundwater wells with >20 mg/L Cl. The model provides an effective means for differentiating groundwater impacted by basin brines versus other contaminants. Using this framework, similar discriminatory tools can be derived for other regions from background water quality data.