Numerical Study of PDL-Induced Fracture-Face Damage Using a Fracturing Mimicator

Gdanski, Rick

doi:10.2118/132918-ms

Cited by 10 publications

(5 citation statements)

References 16 publications

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“…For instance, the flowback chemical data have been as an alternative approach for a quick characterization of the induced fracture network (Gdanski, 2010, Ghanbari et al 2013, Bearinger 2013. Analysis of salt concentration in the flowback water from hydraulically fractured wells in the HRB indicated that the shape of the salt concentration profiles could be used to evaluate the fracture network complexity (Ghanbari et al (2013 and2015).…”

Section: Introductionmentioning

confidence: 99%

Advances in Flowback Chemical Analysis of Gas Shales

Zolfaghari

Tang

Holyk

et al. 2015

SPE Annual Technical Conference and Exhibition

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Recently, flowback chemical analysis has been considered as a complementary approach for evaluating fracturing operations and characterizing reservoir properties. Understanding the source of flowback salts and the mechanisms controlling the water chemistry is essential but also challenging due to the complexity of shale-water interactions. In this study, samples of flowback water and downhole shales are analyzed to investigate the mechanisms controlling the chemistry of flowback water.The water samples at different flowback times and the shale samples are collected from three wells completed in the Muskwa, Otter-Park, and Evie members of the Horn River Basin. The water samples consist of aqueous solution and precipitated salts. The water samples are digested in nitric acid to dissolve the precipitated salts, and are analyzed at both intact and acid-digested conditions using ICP-MS. The flowback salts are weighted and analyzed using XRD and SEM-EDXS. A sequential ion-extraction is performed on the shale samples; and the extracted ions are categorized into three tiers of loosely-, moderately-, and strongly-attached ions.The concentration of monovalent cations in both intact and acid-digested samples is higher than that of divalent cations. Also, the concentration of all cations is higher in the acid-digested samples compared with that in the intact samples. The ratio of divalent cations concentration in the acid-digested samples to that in the intact samples is higher than that for the monovalent cations. This ratio increases for the divalent cations over time, while it remains constant for the monovalent cations. Additionally, for the acid-digested samples the monovalent cations concentration has an initial sharp increase followed by a slower increase at later flowback stages; while the divalent cations concentration increases continuously over time. These results suggest that the majority of the ions in the early flowback water are looselyattached monovalent ions. These ions can be originated from the mixing with in-situ formation brine, dissolution of soluble precipitated salts, or leaching of exchangeable cations from the clay minerals. Similarly, the role of relatively slow water-rock interactions (such as leaching of divalent exchangeable cations, e.g. Ca 2ϩ ,) increases at the later flowback stages. XRD and SEM-EDXS analyzes of the flowback salts indicate that sodium chloride, potassium chloride, and calcium carbonate are the major salts. The sequential ion-extraction reveals that the majority of the monovalent cations are in the loosely-attached tier. However, majority of the divalent cations are moderately-/strongly-attached to the rock. The strongly-attached portion of the ions is determined by acid digestion of the rock sample at the final stage of sequential extraction process. These strongly-attached ions cannot be easily released by hydraulic fracturing and therefore, has small effect on the flowback water chemistry.

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Section: Introductionmentioning

confidence: 99%

Advances in Flowback Chemical Analysis of Gas Shales

Zolfaghari

Tang

Holyk

et al. 2015

SPE Annual Technical Conference and Exhibition

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“…At that time, there was no consideration for variable fracture width, only variable conductivity. Pressure-dependent porosity was also discussed as a part of the fracturing mimicator development (Gdanski 2010). Pressure-dependent porosity and permeability were initially intended to be used for simulating the fracturing process.…”

Section: Porosity Loss and Compression Of Gel Phasementioning

confidence: 99%

Observation of Gel Filter Cake Recovery by Dissolution in Flowback Fluids

Gdanski

Bryant

2012

SPE International Symposium and Exhibition on Formation Damage Control

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Wells completed in tight-gas sands often produce below expectations after fracture stimulation, with gel filtercake damage cited as a major cause of poor performance. These filtercakes have historically been viewed as immobile and insoluble in flowback water. However, recent field observations demonstrated conclusively that borate-crosslinked filtercakes delink and redissolve in flowback water. A fracture cleanup and chemistry simulator (FCCS) was used to discover and develop an appropriate rate law for the dissolution of gel filtercakes in flowback water. The simulator was validated by matching the observed gel content in the flowback waters from a fracturing treatment.Previous work demonstrated that behavior of gel filtercakes in proppant packs from fracturing treatments was more complex than expected. Particularly interesting were recent observations of significant concentrations of gelling agent across several hundred barrels of flowback fluid from a fracturing treatment with good documentation. Ionic composition of the well returns was first matched with the FCCS. Matching of the gel recovery profile required discovery and development of a rate law for dissolution of gel filtercake by water inflowing from the fracture face. Potential rate laws using flow of water down the length of the fracture were not able to match the observed profile. Parametric studies were then conducted and showed a gel displacement regime and a dissolution regime for gel recovery, with the controlling regime dependent on gel phase saturation in the proppant pack. The gel phase saturation in the proppant pack should be 50% or less to be in the dissolution regime for efficient gel recovery.

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“…For instance, analysis of flowback chemical data has been as an alternative approach for a quick characterization of the induced fracture network (Gdanski, 2010, Ghanbari et al 2013, Bearinger 2013. Bearinger (2013) qualitatively correlated the complexity of the fracture network and the salt concentration profiles measured during the flowback process.…”

Section: Introductionmentioning

confidence: 99%

Chemical Analysis of Flowback Water and Downhole Gas Shale Samples

Zolfaghari¹,

Tang²,

Holyk³

et al. 2015

SPE/CSUR Unconventional Resources Conference

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Recently, flowback chemical analysis has been considered as a complementary approach for evaluating fracturing operations and characterizing reservoir properties. Understanding the source of flowback salts and the mechanisms controlling the water chemistry is essential but also challenging due to the complexity of water-shale interactions. In this study, samples of flowback water and downhole shales are analyzed to investigate the mechanisms controlling the chemistry of flowback water.The water samples at different flowback times and the shale samples are collected from three wells completed in the Muskwa, Otter-Park, and Evie members of the Horn River Basin. The water samples consist of aqueous solution and precipitated salts. The water samples are digested in nitric acid to dissolve the precipitated salts, and are analyzed at both intact and acid-digested conditions using ICP-MS. The flowback salts are weighted and analyzed using XRD and SEM-EDXS. A sequential ion-extraction is performed on the shale samples; and the extracted ions are categorized into three tiers of loosely-, moderately-, and strongly-attached ions. Acid digestion is also performed on the shale samples to characterize their elemental composition.The concentration of monovalent cations in both intact and acid-digested samples is higher than that of divalent cations. Also, the concentration of all cations is higher in the acid-digested samples compared with that in the intact samples. Chemical analysis of the flowback water samples suggests that the majority of the ions in the early flowback water are loosely-attached monovalent ions. These ions can be originated from the mixing with in-situ formation brine, dissolution of soluble precipitated salts, or leaching of exchangeable cations from the clay minerals. Similarly, the role of relatively slow water-shale interactions (such as leaching of divalent exchangeable cations, e.g. Ca 2ϩ ) increases at the later flowback stages. XRD and SEM-EDXS analyzes of the flowback salts indicate that sodium chloride, potassium chloride, and calcium carbonate are the major salts. The sequential ion-extraction reveals that the majority of the monovalent cations are in the loosely-attached tier. However, majority of the divalent cations are moderately or strongly attached to the rock. The strongly-attached portion of the ions is determined by acid digestion of the rock sample at the final stage of sequential ion-extraction process. These stronglyattached ions cannot be easily released by hydraulic fracturing and therefore, has small effect on the flowback water chemistry. Flowback chemical analysis indicate that sodium is the major ion in the flowback water and its concentration is higher than the potassium concentration. While, according to the results of acid digestion of rocks, potassium is the major constituent of our shale samples and its concentration is about five times higher than the sodium concentration. Moreover, although barium is not a major constituent of our shale samples (ϳ0.05%), the concentratio...

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Numerical Study of PDL-Induced Fracture-Face Damage Using a Fracturing Mimicator

Cited by 10 publications

References 16 publications

Advances in Flowback Chemical Analysis of Gas Shales

Advances in Flowback Chemical Analysis of Gas Shales

Observation of Gel Filter Cake Recovery by Dissolution in Flowback Fluids

Chemical Analysis of Flowback Water and Downhole Gas Shale Samples

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