Breaker Concentration Research Articles

Design and development of instant linear gel for coal bed methane gas operations

Linear gel fracturing fluids are expressed with an extensive range of materials/polymers in an aqueous base. Earlier we developed fracturing linear gel with fossil diesel, bio-diesel and also used suspending anti-settling agents and emulsifiers. Here we report on a novel and an efficient method for the preparation of linear gel direct mix with water, guar gum and sodium acetate together instantly. In this research work, we used water instead of diesel without any need to mix anti-settling agents, suspending agents, emulsifiers that resulted in 30 viscosity linear gel. The degradation pattern observed from the breaker test showed that a reduction in gel viscosity depends on time, temperature & breaker concentration. Ammonium per sulphate or Ammonium per oxidisulphate and enzyme-G were used for oxidation purpose to break the gel gradually at a particular static temperature. Observations from experiments revealed that a small concentration of breaker provides rapid break compared to oxidative breakers. This article, designing of fracturing fluids describes how to use the fluid's viscosity generated by the gelling agents like guar gum for CBM operations.

Delayed Breaker Systems To Remove Residual Polymer Damage in Hydraulically Fractured Reservoirs.

Hydraulic fracturing is a widely used technology to enhance the productivity of low-permeability reservoirs. Fracturing fluids using guar as the rheology builder leaves aside residual polymer layers over the fractured surface, resulting in a restricted matrix to fracture flow, causing reduced well productivity and injectivity. This research developed a specialized enzyme breaker and evaluated its efficiency in breaking linear and cross-linked guar-polymer gel as a function of time, temperature, and breaker concentration targeting a high-temperature carbonate reservoir. The study began with developing a high-temperature stable galacto-mannanase enzyme using the “protein-engineering” approach, followed by the optimization of fracturing fluids and breaker concentrations measuring their rheological properties. The thermal stability of the enzyme breaker vis-à-vis viscosity reduction and the degradation pattern of the linear and cross-linked gel observed from the break tests showed that the enzyme is stable and active up to 120 °C and can reduce viscosity by more than 99%. Further studies conducted using a high-temperature high-pressure HT-HP filter press for the visual inspection of polymer cake quality, filtration loss rates, and cake dissolution efficiency showed that a 6 h enzyme treatment degrades the filter cake by 94–98% compared to 60–70% degradation in 72 h of the natural degradation process. Coreflooding studies, under simulated reservoir conditions, showed the severity of postfracture damage (up to 99%), which could be restored up to 95% on enzyme treatment depending on the treatment protocol and the type of fracturing gel used.

Experimental simulation of proppant permeability in hydraulic fracturing at extended time under bottom-hole conditions

During hydraulic fracturing treatment, huge quantities of gel are pumped into the formation to initiate the fracture, maintain it open and transport the proppant. The fracture dimensionless conductivity (Fcd) is a key parameter to optimize the fracturing design, to estimate the productivity Index (PI) and the folds of increase (FOI). However, these parameters are affected by the gel residues which decrease the fracture conductivity; thus, the proppant cleanup is a very important step to avoid additional damage caused by fracturing fluid due to high gel concentration and the extended time of gel staying in the fracture before cleanup. Throughout the life of Hassi Messaoud, Algeria field, hydraulic fracturing technique has been aggressively used mainly in four producing formations in the Cambrian, with hard formation characteristics, an average permeability range and low reservoir pressure (0.15–0.45 psi/ft) and high stress value between 6000 and 9000 psi. In this paper, an experimental simulation is applied using a self-made cell to determine the effect of different parameters on the fracture conductivity under various bottom-hole conditions where different variables were used: effect of Proppant type, guar gel concentration, temperature, breaker concentration and closure pressure at extended time. An important drop in fracture conductivity was observed varied between 10 and 80% under stresses at interval of 2000 psi and 8000 psi, gel concentration up to 200 lb/1000 gal at extended time and temperature.

Development of Instant Linear Gel for Coal Bed Methane Gas Operations

Previously we prepared fracturing linear gel with fossil diesel, bio-diesel and also used suspending, anti-settling agents and emulsifiers. But through this research, a novel and efficient method for the preparation of linear gel directly mixed with water, guar gum and sodium acetate together instantly. In this instead of diesel, we used water and no need to mix anti-settling agents, suspending agents, emulsifiers that resulted in 30 viscosity linear gel. Ammonium persulphate or Ammonium peroxidisulphate and enzyme-G are used for oxidation purposes to break the gel gradually at a particular static temperature. The degradation pattern observed from the breaker test showed that a reduction in gel viscosity depends on time, temperature & breaker concentration. Observations from experiments revealed that a small concentration of breakers provides rapid break compared to oxidative breakers. This article, designing of fracturing fluids describes how to use the fluid's viscosity generated by the gelling agents like guar gum for CBM operations.

Experimental Evaluation of Oxidizing Breakers for a Polyacrylamide-Based Re-Crosslinkable Preformed Particle Gel

Re-crosslinkable preformed particle gel (RPPG) is a newly developed conformance control agent that can reassemble as an integrity after swelling in water. However, the RPPG has the potential to plug the injection facilities or wellbore if a treatment is not properly designed. This study focuses on selecting and evaluating the oxidizing breakers that can effectively degrade the RPPG. Bottle tests were conducted by immersing the re-crosslinked RPPG in the breaker solutions. The RPPG weight change was measured with time to analyze the breaking process. Four types of oxidizing breakers, NaClO, Ca(ClO)2, heat-activated Na2S2O8, and NaOH-activated Na2S2O8 were examined. The effect of factors, including breaker concentration, temperature, RPPG concentration on the gel breaking rate and completeness, was investigated. According to the results, three of the breakers were proven effective, excluding the Ca(ClO)2, which impaired the breaking process by generating a compact cover on the surface of RPPG. The NaOH-acti...

Simulating yield stress variation along hydraulic fracture face enhances polymer cleanup modeling in tight gas reservoirs

Several measures have been taken to enhance the supply of fossil fuel energy in the United States during the last decades, some of which include the development and exploitation of very low permeability and low porosity reservoirs in challenging environments. These reservoirs usually require enhanced stimulation techniques such as multi-stage hydraulic fracturing and horizontal drilling to increase the contact between the wellbore and the producing formation for a profitable recovery. During the fracturing process, fluids are pumped into the reservoir under high pressure, to create fractures through which gas flows back to the earth's surface during production. However, a layer of concentrated polymer forms on the fracture faces limiting the loss of fluid to the formation during injection while impairing fracture conductivity during production. The inadequacy of the fracture conductivity after a fracture treatment using cross-linked fluids is typically due to poor degradability of our polymers, proppant crushing, clay swelling in the case of incompatible fluids and formation damage. The objective of this work is to develop a fracture cleanup model that simulates the rheological variations of filter cake and degraded fluids inside the fracture by including the effect of breaker and polymer concentration on the yield stress of the fracturing fluid that result in variations in capillary pressure, fracture conductivity, fracture length and formation damage during the cleanup process in unconventional tight gas formations.A dynamic 2-D, three-phase IMPES simulator, incorporating a yield-power-law-rheology (Herschel-Buckley fluids), has been developed in MATLAB to simulate variations in rheological properties of degrading fracturing fluids versus time and investigate the influence of several major parameters on the fracture cleanup process. These parameters include variations in polymer concentration along the fracture length, breaker concentration variations, fracture conductivity, fracture length, capillary pressure and formation damage with a novel correlation between yield stress and breaker concentration, which enhances post – fracture well performance prediction in tight gas reservoirs. The three phases simulated here include water, gas and the gel phases.Simulation of the injection of fracturing fluids and fluid imbibition during the shut-in time indicated that for tight gas formations, fluid recovery increases with increasing shut-in time, increasing fracture conductivity and fracture length irrespective of the yield stress of the fracturing fluid. Simulation of the production phase highlighted that increasing the capillary pressure to a maximum of 350.10 psi resulted in a 10.4% decrease in cumulative gas production. The rate of increase in the yield stress of the fracturing fluid along the fracture face is proportional to the square of the volume of fluid loss to the formation. Production will be enhanced significantly with increasing breaker concentration indicating that simulation of the yield stress variation along the fracture face presents a more realistic scenario of the fracture cleanup process rather than assuming a constant value since the fluid loss to the formation and the polymer concentration distribution decrease with fracture length.

Permeability evolution study after breaking of friction reducer in near fracture matrix of tightgas reservoir

Hydraulic fracturing is generally required for tightgas formation with low matrix permeability to achieve economic production rate. Slickwater fracturing is one of most commonly used technology. Friction reducer is the primary component of this fluid. During fracturing, million gallons of friction reducer fluid are pumped downhole to initiate fractures, and lots of fluid would filtrate into formation matrix. Due to the small pore size of tightgas reservoir, breaking of the friction reducer fluid is required to minimize formation damage and improve the conductivity in fracture. However, this performance in tightgas is not clear.In this paper, tightsand samples were treated with a friction reducer and a breaker to simulate the filtration process during hydraulic fracturing. Three breaking scenarios were proposed and studied correspondingly. Over balance breaking resulted in higher permeability regain than balance and under balance breaking, which means less formation damage to the near fracture matrix. The short sample has a full recovery of permeability with over balance breaking and it is higher than that with balance and under balance breaking. With over balance breaking, 0.012wt% breaker recovers 79.5% permeability, and the permeability regain increases with higher breaker concentration. The permeability regain of longer sample is improved, up to 116.3%. With under balance breaking, 0.1vol% friction reducer shows 81.6% permeability regain. Lower concentration friction reducer achieves a higher permeability regain. The reasons can be attributed to pore blocking effect and wettability alteration introduced by the friction reducer and breaker. The emulsion particle size in the friction reducer solution is found to overlap with the pore size distribution of tightgas sandstone. Therefore, it was able to block the matrix pores in tightsand after treated with the friction reducer and breaker. The contact angle on sample surface was changed from 24.3° to 81.1° in average.

Evaluating The Effect of Temperature and Polymer Concentration on Properties of Hydroxyethyl Cellulose Gravel Pack Fluid

The commercial success of petroleum wells depends greatly on the type of completion, especially the choice of gravel packing fluid system for wells with gravel pack completions. Currently several polymers are in use to viscosify gravel pack fluids. These polymers are expected to exhibit acceptable properties such as good solubility, viscosity yield, rheology, sand carrying capacity, thermal stability, break profile, low residue content and others, to match the job requirements, in order not to jeopardize the sand control process or cause hydrocarbon production impairment. Hydroxyethyl cellulose (HEC), one of the most commonly used polymers used in formulating gravel pack fluids has so many good qualities, such as very low solid residues and easy clean out. In this paper, gel break time was investigated for 40lbs/1000gal and 60lbs/1000gal HEC polymer concentrations at 140°F, 160°F and 180°F, using Sodium Persulfate as gel breaker at concentrations of 1.0lbs/1000gal, 5.0lbs/1000gal, 10.0lbs/1000gal and 20.0lbs/1000gal. The proppant carrying capacity at different temperatures was also investigated. Test results indicated that gel break is a function of temperature, breaker and polymer concentrations. At higher temperatures and higher breaker concentrations, gel break is faster, but slower for higher polymer concentration.

Preparation of linear frac concentration with 4-Vinyl-2,6-Dimethoxyphenol

We studied about 4-vinyl-2,6-Dimethoxyphenol is a solvent (canola oil), it was produced from seed of several variety of the rape plant, those plants, namely Brassica napus L (or) field mustard, turnip rape it is also used as a source of Biodiesel. Canola oil is used as a solvent in linear frac concentration. Anti-settling agents, neutralizing agents like sodium hydroxide (or) sodium acetate (or) sodium bicarbonate will maintain the pH, mixed together formed frac concentration. So this study focuses on the way to mix the fracturing fluid, compositions of fracturing fluid how to conduct Linear (gel) and breaker test. These polymers are dry powders that hydrate or swell when mixed with an aqueous solution and form a viscous gel. Degradation pattern observed from the breaker test showed that reduction in gel viscosity depends on time, temperature and Breaker concentration. This linear gel will use in Oil and gas wells during fracturing on-shore operations for (CBM or Coal-Bed Methane gas zones)to enhanced the oil & gas production.

Novel Oxidizing Breaker for High-Temperature Fracturing

Summary A novel oxidizing breaker system has been developed for fracturing fluids at high temperatures. Below 200°F, the system is not active, but above 200° F, the oxidizing system aggressively attacks the polysaccharide backbone of the fracturing fluids, resulting in a complete break of the crosslinked fluids. In the presence of a gel stabilizer, an intermediate, reactive oxidizing species is formed. The result of this formation is a delayed, soluble, high- temperature oxidizing system. Controlled viscosity reduction at 200 to 300°F in crosslinked gelled fluids with and without a gel stabilizer will be demonstrated. Testing included model 50 viscosity profiles, high- temperature static break tests, and conductivity testing. Results from all testing showed the effect of oxidant concentration in producing a predictable, controlled break of the thermally stabilized crosslinked systems. Data were obtained in low-pH and high-pH Zr-crosslinked fluids as well as in borate-crosslinked fluids. The delayed mechanism of the new breaker system provides fluids with excellent crosslinked viscosity properties at early times with predictable, long-term viscosity reductions. Case histories show that the breaker system can be used throughout the treatment in the pad fluid, proppant-laden fluid, and flush. This article provides data that allow significant improvements in job design. The operations engineer can obtain predictable, controlled gel degradation by using the data provided for temperature, gel type, gel stabilizers, and breaker concentration. The results are optimized treatment designs with rapid fluid recovery, improved proppant-bed conductivity, and increased well productivity.

Breaker Concentrations Required To Improve the Permeability of Proppant Packs Damaged by Concentrated Linear and Borate-Crosslinked Fracturing Fluids

Summary The concentrations of an oxidative breaker required to reduce significantly the proppant-pack permeability damage caused by aqueous hydraulic fracturing fluids have been determined. Long-term, proppant-pack permeability testing was used to evaluate linear • and borate-crosslinked gels. Results indicate that increasing the breaker concentration can reduce proppant-pack permeability damage very effectively.

Encapsulated Breaker for Aqueous Polymeric Fluids

SummaryConventional breakers reduce fracturing-fluid viscosity much too rapidly, even at moderate temperatures (140 to 200°F), to be used at the high concentrations required to degrade polymers within proppant packs. A delayed-release, encapsulated breaker was developed that permits the use of high breaker concentrations and thus significantly increases fracture conductivity.

Polysaccharide Derivatives Provide High Viscosity and Low Friction at Low Surface Fluid Temperatures

A relatively new, low-damage aqueous thickener with improved fracturing fluid properties is described. The polysaccharide derivative is effective in continuous mixing with low surface fluid temperatures and achieves high viscosity and low friction much more rapidly than conventional thickeners. Introduction Continuous mixing of gelled aqueous fracturing fluids is desirable because it reduces treating time and equipment and storage requirements, and eliminates batch mixing of large volumes of fluid that might not be used. In the past, the time required for conventional thickeners to achieve friction reduction and viscosity, particularly with cold fluids, has limited continuous mixing as a treating technique during cold weather and in shallow wells with low bottom-hole temperatures. New, low-residue polysaccharide derivatives have now been developed, however, that achieve high viscosity and low friction much more rapidly than conventional thickeners. For example, in 40 degree water, the new thickener can reduce friction up to three times more effectively than the conventional thickeners and can also provide viscosities up to four times greater. The advantages of low-residue fluids for minimizing damage and, hence, potential losses in production are discussed. The proper use and design criteria for low-residue systems are examined. Continuous mixing with the thickener permits using higher breaker concentrations to reduce shut-in times, thus providing faster, more effective well cleanup. In conjunction with the new gelling agent, additives such as clay control agents and new surfactants are used to shorten cleanup times by as much as one-half and to increase fracturing fluid recovery two to three times over conventional water-based treatments. It appears to be a growing opinion in the industry that short shut-in times for minimizing fluid retention may be a key to improved production by fracturing. History During the past several years, many new fracturing fluids have been developed. In many cases, these fluids met specific requirements such as high temperature stability, low formation damage, more rapid cleanup, or ultrahigh viscosity. Guar gum has been an effective gelling agent in fracturing fluids for many years. In most aqueous-base conventional fracture treatments, guar gum is still the thickener most commonly used. Guar gum generally meets the basic requirements of an efficient and economical fracturing fluid. Guar gum gives low friction pressures, good viscosity in a variety of brines, low fluid loss, pressures, good viscosity in a variety of brines, low fluid loss, and effective breakdown control following the treatment. The fluid-loss control of guar gum is particularly effective as compared with other aqueous thickeners. The major objection to guar gum has been an insoluble residue component that potentially could cause damage. Although petroleum guar products are more highly refined than other guar products, they contain almost 10 percent residue. Guar gum residue may or may not be detrimental to formation permeability or fracture conductivity, depending on conditions. permeability or fracture conductivity, depending on conditions. If damage occurs to permeability or fracture conductivity, the effect on productivity should be based on the well and treating conditions. Pye and Smith and Cooke have discussed the effect of guar gum and fluid-loss additives on formation damage and damage to fracture conductivity. JPT P. 1067