Method for Delivering Frac Fluids and Additives

A method for the controlled delivery of a fracturing fluid to a well bore comprises formulating an aqueous base fluid such that it meets or exhibits desired physical and chemical characteristics for an optimal fracturing fluid. The formulation of the aqueous base fluid max involve commingling one or more sources of waste water with a source of fresh water followed by controlled injection of one or more additives. This process is substantially completed prior to delivering the aqueous base fluid to the well site. This allows the delivery of an optimal volume of the aqueous base fluid with homogeneously blended additives to the well bore.

SUGGESTED CITATION

Method for Delivering Frac Fluids and Additives, E. J. Termine and R. Richie, United States Patent Application No. 2010/0059226.
Available at: http://terminegroup.com/archives/379

BACKGROUND OF THE INVENTION

[0002] Fracturing is the process of creating fractures in oil and gas formations to stimulate or increase production in oil and gas wells. The frac or fracturing operation involves the injection of fracturing fluid into the wellbore at sufficient pressures, flow rates and volumes to fracture the surrounding formation. The fracturing fluid may comprise a base fluid, such as water or gels, and a variety of additives including polymers, friction reducers, cross-linkers, anti-scaling agents, proppants and biocides. The fracturing forms a conductive flow path for hydrocarbons. However, once the fluid pressure in the fracture drops, the fracture closes. Therefore, proppants are injected with the base fluid to fill the fracture and prop it open. Materials used for proppants may include sand, ceramics and glass beads.

SUMMARY OF THE PRESENT INVENTION

[0003] The one or more embodiments of the invention facilitate the delivery of optimal volumes of a fracturing fluid containing optimal concentrations of one or more additives to a well bore. Conventional practice involves pre-staging large volumes of fracturing fluid with ad hoc additions of one or more additives. This results in poor or non-homogeneous dispersion of the additives, and frequently results in wasteful, non-optimal additive concentrations. In contrast, the one or more embodiments of the invention allow for accurately and precisely controlling the volume of the fracturing fluid delivered, at high flow rates, to the well bore. Advantageously, the fracturing fluid may also contain accurately and precisely controlled concentrations of one or more additives. In one or more embodiments, the concentration of the additives may be extremely small, even trace amounts, when compared to the large volume of the aqueous base fluid in which the additives are dispersed. One or embodiments of the invention disclose repeated testing and analysis of an aqueous base fluid which is utilized in formulating the fracturing fluid, in-line and prior to delivery to the well site. As a consequence of this testing and analysis, accurate adjustments to the physical and chemical characteristics of even large volumes, typically hundreds of thousands of gallons, of the aqueous base fluid may be made through the introduction of precise concentrations one or more additives. Since the additives may be blended in-line in the aqueous base fluid, prior to its delivery to the well site, the additives are homogeneously dispersed in the aqueous base fluid by the time the aqueous base fluid is used to formulate the fracturing fluid. In one embodiment of the invention, only optimal volumes of the aqueous base fluid are delivered to the well site. The testing and analysis continues at the well site, and also during the pumping of the aqueous base fracturing fluid into the well bore. Adjustments to the additive concentration may also be made to large but optimal volumes of the fracturing fluid pumped at high flow rates, from 5 to 150 bbls/minute, such that only optimal concentrations of the additives are utilized in the fracturing operation.

[0004] In one embodiment of the invention, a method for the controlled delivery of a fracturing fluid to a well bore comprises determining one or more available sources of an aqueous base fluid for the fracturing fluid. The one or more available sources of the aqueous base fluid comprises lakes, rivers, ponds, creeks, streams, well water, fluid effluent from industrial processes, brines, processed fluids, flowback fluids, pit water, spudder water, and other waste waters or fluids. One or more samples of each source may he individually tested to determine its physical and chemical characteristics, followed by comparing the physical and chemical characteristic data of each available source with predetermined physical and chemical characteristic data for an optimal fracturing fluid to identify suitability of the fluid source for a fracturing operation. A source of aqueous base fluid that compares favorably to the optimal fracturing fluid may be selected for delivery to the fracturing operation at the well site. The aqueous base fluid may be transported to one or more fracturing fluid tanks. The aqueous base may be transported by trucking or using a pumping mechanism with one or more pipelines connecting the pumps to the fracturing fluid tanks. In another embodiment, the one or more fracturing fluid tanks are grouped into one or more sets, wherein each set contains one or more fracturing fluid tanks. One set of fracturing fluid tanks may be positioned proximate a source of the aqueous base fluid for conveniently delivering the aqueous base fluid to a second set of fracturing fluid tanks that may be located proximate a well site. In another embodiment of the invention, the aqueous base fluid may be pumped from the source to a first set of fracturing fluid tanks, and thereafter pumped to a second set of fracturing fluid tanks.

[0005] One or more samples of the aqueous base fluid may be tested in the fracturing fluid tanks to determine its physical and chemical characteristics. The physical and chemical characteristics may comprise flow rate, pH, viscosity, ionic strength, volume, homogeneity, specific chemical concentrations, density, crystallization temperature, biocide demand and combinations thereof. Measurement of the physical and chemical characteristics is made using flow meters, pH meters, conductivity meters, and other instruments known in the art. These physical and chemical characteristic data may be then compared to the predetermined physical and chemical characteristic data for the optimal fracturing fluid.

[0006] In the event of a failed comparison, that is, if the physical and chemical characteristics of the sampled fluid differs from those of the optimal fracturing fluid, one or more additives, may be continuously introduced into the aqueous base fluid until it achieves the predetermined physical and chemical characteristics. Thus, for instance, if the aqueous base fluid is found to have scaling properties, anti-scaling additives may be introduce to the aqueous base fluid. On the other hand, if the aqueous base fluid is found to be corrosive, anti-corrosive chemicals may be introduced to the aqueous base fluid. The additives may be selected from a group comprising biocides, pH modifiers, corrosion inhibitors, friction reducers, scale inhibitors, oxygen scavengers, hydrogen sulfide, oxidizing agents, viscosifiers and combinations thereof. In one embodiment of the invention, the biocide comprises an oxidizing biocide. In another embodiment, the oxidizing biocide comprises a bromine biocide. The additives may be blended into the aqueous base fluid until they are homogeneously dispersed. The aqueous base fluid blend may be delivered to the well site for the fracturing operation. At the well site, the aqueous base fluid blend is used to formulate the fracturing fluid. Formulation of the fracturing fluid involves introduction of additives and/or one or more proppants to the aqueous base fluid blend. An optimal volume of the fracturing fluid is pumped at high flow rates to the well bore for fracturing the surrounding formations. The optimal volume of the fracturing fluid further comprises an optimal concentration of the homogeneously dispersed additives. In one embodiment of the invention, the optimal volume of the fracturing fluid is pumped to the well bore at from 5 to 150 bbls/minute. In another embodiment of the invention, the optimal volume of the fracturing fluid is pumped to the well bore at from 15 to 120 bbls/minute. In yet another embodiment of the invention, the optimal volume of the fracturing fluid is pumped to the well bore at from 60 to 100 bbls/minute.

[0007] In another embodiment of the invention, the aqueous base fluid from two or more of the sources may be commingled in the event the individual sources are unsuitable for the fracturing operation. At least one of the commingled sources may comprise water or fluids from another source, such as, spudder water, pit water, flowback fluid or other waste fluids generated during oil and gas production operations. These fluids have to be disposed and the disposal of the fluids entails transportation costs. By recycling these fluids (by commingling it with another source, typically a source of fresh water) as a base fluid for the fracturing operation, the well operator may save disposal costs, and have a readily available supply of the aqueous base fluid. It may also be possible to cut down on the huge volumes, typically tens of thousands of barrels, of the fresh water or frac water that is required for fracturing the wells, since the fresh water is now commingled with the easily available waste fluids.

[0008] The commingled aqueous base fluid may be transported to the fracturing operation in a first set of fracturing fluid tanks in the event the commingled aqueous base fluid is identified as suitable for the fracturing operation. One or more samples of the commingled aqueous base fluid may be tested in the first set of fracturing fluid tanks to determine its physical and chemical characteristics. In another embodiment of the invention, one or more samples of the commingled aqueous base fluid may be tested in-line while it is pumped to a first set of fracturing fluid tanks.

[0009] The physical and chemical characteristic data of the commingled aqueous base fluid may be compared to the predetermined physical and chemical characteristic data for the optimal fracturing fluid. If the characteristics are comparable, the commingled aqueous base fluid may be transported to the well site. If the physical and chemical characteristics of the commingled aqueous base fluid are not comparable to the optimal fracturing fluid, one or more additives may be continuously introduced into the commingled aqueous base fluid to achieve the same characteristics. The one or more additives may be blended into the commingled aqueous base fluid until it is homogeneously dispersed.

[0010] In one embodiment of the invention, the additives may be introduced in a controlled manner by one or more metering pumps. The addition of additives may be conducted in real-time. The metering pumps may be monitored at a control center manually or automatically. The control center may comprise one or more computers comprising a computer program product for automatically adjusting the dosage rates of the additives. The dosage rate may depend on a formation to be fractured, the conditions of a specific well and the physical and chemical characteristics of the commingled aqueous base fluid. The adjustments to the dosage rates may be made on-the-fly. The adjustments to the dosage rates may be made as-needed. The monitoring of metering pumps and adjustments to the additive dosage rate may also be conducted in real-time.

[0011] In one embodiment of the invention, a bromine-based biocide may be added to the commingled aqueous base fluid if it is determined to contain bacterial or other microbial living organisms. The bromine biocide is homogeneously dispersed within the commingled aqueous base fluid. The bromine biocide may be added in-line during pumping to the second set of fracturing fluid tanks or at the second set of fracturing fluid tanks, but prior to transportation to the well site. This ensures adequate bacterial/microbial “kill time” for the biocide to effectively eliminate these organisms. The addition of the bromine biocide may be automated.

[0012] The commingled aqueous base fluid blend may be delivered to a second set of fracturing fluid tanks when the commingled aqueous base fluid blend achieves the predetermined physical and chemical characteristics. One or more samples of the commingled aqueous base fluid blend may be collected, monitored and tested in-line during delivery to the second set of fracturing fluid tanks. The physical and chemical characteristics of the commingled aqueous base fluid blend may be continuously adjusted by introducing additives in-line and/or at the second set of fracturing fluid tanks. The second set of fracturing fluid tanks containing the commingled aqueous base fluid blend may be transported to the well site when the commingled aqueous base fluid blend achieves the predetermined physical and chemical characteristics.

[0013] In one embodiment of the invention, the second set of fracturing fluid tanks may be located at a distance from the well site. The commingled aqueous base fluid blend may he transported from the second set of fracturing fluid tanks to a third set of fracturing fluid tanks located at the well site when the commingled aqueous base fluid blend achieves the predetermined physical and chemical characteristics.

[0014] One or more samples of the commingled aqueous base fluid blend may be tested at the well site to determine its physical and chemical characteristics. The testing at the well site may be carried out in real-time using one or more simplified field test kits. Based on the testing results, one or more additives, such as viscosifiers, and/or one or more proppants may be added to, or their concentrations adjusted in, an optimal volume of the commingled aqueous base fluid blend to achieve the predetermined physical and chemical characteristics. The additives and/or proppants may be blended in the commingled aqueous base fluid to form the fracturing fluid. The one or more proppants further comprise sand particles, resin-coated particles, mineral fibers, ceramic particles, glass beads, aluminum pellets and mixtures thereof. The commingled aqueous base fluid blend may be pumped to a hopper or mixing equipment for admixing with the additives and/or proppants.

[0015] Conventional or existing practice involves introduction of one or more additives to the formation independent of the fracturing operation. The additives are added at the production site either directly into the well bore or by mixing in a hopper or mixing equipment along with large volumes of the fracturing fluid, proppants and other substances needed in the fracturing operation. This results in inadequate dispersion of the additives in the fracturing fluid and the blend is not homogeneous. The process also does not allow for the monitoring and feedback needed to control the rate of addition of the additives to the fracturing fluids. The well operators, therefore, do not have control over the additive concentration delivered to the formation, or whether an effective amount of additives has been added, or whether too much additives have been added in the fracturing operation. This results in inadequate or excessive concentrations of additives being used in the frac or fracturing operation. This adversely impacts the fracturing operation, resulting in loss of production. Furthermore, large volumes of one or more fracturing fluids are required in the fracturing operation since adequate information on the composition, flow rates and/or interaction between the one or more fracturing fluids and the one or more additives is not easily available. The well operators typically employ larger than necessary fracturing volumes in an attempt to overcome this lack of information. All of this results in an inefficient and costly process. There is also an environmental cost associated to this, since the flowback fluids return from the well bore after the fracturing operation is completed and have to be cleaned up, and proper disposal of certain toxic additives comprising biocides and surfactants has to be ensured, at the end of the fracturing process. Embodiments of the invention teach an efficient and cost-effective method for the controlled delivery of fracturing fluids to the well bore.
___________________________________________________________________________________________________________

[Full Text Not Available]

Written by

Dr. Enrico J. Termine is a senior executive and scientist with thirty years of experience in business leadership, research & development, product engineering, marketing, and manufacturing. He has consulted for a variety of industrial and legal clients on engagements involving valuations, due diligence assignments, market research reports, strategy development reports, science and technology assessments, and root cause investigations. Dr. Termine is a bromine chemistry expert. He specializes in oilfield applications, flame retardant plastics, industrial and recreational water treatment and disinfection, specialty and fine chemicals, polymer additives, plastics, and organic synthesis for life science molecules and advanced materials. Dr. Termine earned both his Bachelor of Science in Chemistry and his Ph.D. in Organic Chemistry from the University of Miami. He has collaborated on more than 38 patents and publications. His technical contributions are useful in consumer electronics; for petroleum and petrochemical processing; in transportation and industrial products; in healthcare; for industrial and household disinfection; and in building and construction materials.

No Comments Yet.

Leave a Reply

Security Code: