Advanced Sandstone-Acidizing Designs With Improved Radial Models

Gdanski, Rick; Shuchart, Chris E.

doi:10.2118/52397-pa

Cited by 40 publications

(23 citation statements)

References 17 publications

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“…Among these problems are: decomposition of clays in HCl acids, the presence of carbonate can cause the precipitation of calcium fluorides (CaF 2 ), HCl-sensitive clays (eg., illite) can cause formation damage, the high reaction rate and corrosion rate at high bottomhole temperatures (Shuchart and Gdanski 1996;Thomas et al 2001), and mixing between various stages of the treatment may occur during the treatment by mud acid (Gdanski and Shuchart 1998).…”

Section: Problem Associated With Mud Acid Treatmentsmentioning

confidence: 99%

Acidizing Sandstone Formations Using a Sandstone Acid System For High Temperatures

Zhou

Nasr‐El‐Din

2013

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Regular mud acid mixtures have been extensively used to stimulate sandstone formations; however, the use of this acid in a deep well has some major drawbacks, including high and uncontrolled reaction rate and corrosion to well tubulars. A single stage sandstone acid system (HF and a phosphonic acid) has been developed as an alternative to mud acid. Carbonate minerals in sandstone formations can cause formation damage. Therefore, there is a need to remove the carbonates to enhance the performance of this sandstone acid system.In this study, the single stage sandstone acid systems with different HF concentration were examined to stimulate sandstone formation at high temperature. Berea (5 wt% clays) and Bandera (11 wt% clays) sandstone cores were used in the coreflood experiments. Coreflood experiments on sandstone cores were conducted at 300°F at a flow rate of 2 cm 3 /min. The concentrations of Si, Ca, Al, Mg, and Fe in the core effluent samples were analyzed using Inductively Coupled Plasma (ICP). 0.6M GLDA (pH= 3.8), 0.6M HEDTA (pH =3.8), and 9 wt% formic acid solution were evaluated to remove the carbonate minerals from Bandera sandstone cores.Coreflood experiments showed the sandstone acid systems enhanced the permeability of Berea sandstone cores, and the optimum injection volume is 2.5 PV to keep the integrity of the cores at 2 cm 3 /min and 300°F. This acid system damaged Bandera sandstone cores severely at 300°F, which contain 16 wt% dolomite, and 10 wt% illite. Analysis of core effluent samples indicated that there was CaF 2 precipitate in the core when the acid systems were pumped without preflush. Therefore, calcium carbonate in Bandera sandstone cores should be removed with preflush. GLDA, HEDTA and formic acid (9 wt%) were compatible with Bandera sandstone cores at low pH value, and formic acid was much more effective in remove carbonate in Bandera sandstone cores. IntroductionThe objective of sandstone reservoir stimulation is to remove the damage caused to the production zone during the drilling or completion process and improve well performance. Three main stages are involved, including preflush, main acid stage, and postflush. Mud acid has been extensively used as main acid in the field with variable success rates (Simon and Anderson 1990). The ideal stimulation fluid should remove the near-wellbore damage without depositing precipitates in the formation, and preventing well production declines due to solids movements.Sandstone acidizing is a complex operation because of the treatment involves flow and reactions in porous media where the reactive chemicals contact a wide range of minerals. The formation contains various amounts of quartz, clays, as well as carbonates. Clay minerals are extremely small, platy-shaped materials that may be present in sedimentary rocks as packs of crystals. The types, volumes, and morphologies of the clays will determine the success or failure of the sandstone acidizing treatments. The clay minerals can be classified into four main groups: (1) kaolinite group, (2) chl...

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Section: Problem Associated With Mud Acid Treatmentsmentioning

confidence: 99%

Acidizing Sandstone Formations Using a Sandstone Acid System For High Temperatures

Zhou

Nasr‐El‐Din

2013

All Days

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“…The CIR scale developed for acidizing was based on the rate of acid attack on clays, which released aluminum into solution and caused amorphous silica gel to form. 7 The rate of attack was determined by adjusting the value of the rate constant in the rate law for that attack. This same approach was used to develop the high-pH CIR scale.…”

Section: → +mentioning

confidence: 99%

“…6 Even with these developments, the powerful effect of ion exchange transformation of brines used for stimulation and remedial workovers escaped broad notice until recently. 7,8 In a similar fashion, the powerful effect of clay acidity has only slowly been brought into proper awareness.…”

Section: Introductionmentioning

confidence: 99%

High-pH Clay Instability Rating

Gdanski

2002

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fax 01-972-952-9435.References at the end of the paper. AbstractIt is commonly understood that clays have surface hydroxyls that are available for various interactions. The magnitude of the interactions possible because of the natural acidity that clays possess has been previously demonstrated. 1 Laboratory experiments using a 3-ft Hassler sleeve and unconsolidated sand/claypacked columns demonstrated that the pH profile of buffered and unbuffered high-pH fluids can be readily understood as the result of two dominant mechanisms. The first mechanism is neutralization by the natural clay acidity. The second mechanism is the attack of hydroxide on clays and is demonstrated in this paper. The rate of hydroxide attack is temperature, clay, and pH dependent. The rate constants were used to develop a high-pH Clay Instability Rating (CIR) for the clays tested. The impact of CIR on injected-fluid pH profiles was numerically demonstrated with the new model for both linear and radial flow. These two geometries are relevant to leak-off during frac-packs (linear) and for drill-in fluids and matrix treatments (radial).

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“…Gdanski and Scuchart (1998) have shown that essentially all clays are unstable in HCl above 300 o F. The ideal stimulation fluid would remove the near-wellbore damage without depositing precipitates in the formation, and preventing well production declines due to solids movements. Martin (2004) has showed that it was possible to stimulate sandstone formation without subsequent need for HF acid.…”

Section: Introductionmentioning

confidence: 99%

Novel Environmentally Friendly Fluids to Remove Carbonate Minerals from Deep Sandstone Formations

2011

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Carbonate minerals are present in sandstone formations. These minerals are either introduced to the formation during drilling/completion operations or naturally present in the rock. There is a need to remove these carbonates to enhance well performance. This especially true if there is a need to use HF-based fluids to prevent the precipitation of calcium and magnesium fluorides.In this study, we introduced GLDA (L-glutamic acid-N,N-diaceticacid) a new environmentally friendly chelate to remove carbonate minerals from sandstone formations. We also compared its performance with available chelates like EDTA (ethylenediaminetetraaceticacid) and HEDTA (hydroxyethylenediaminetriaceticacid). Berea (5 wt% clays) and Bandera (11 wt% clays) sandstone cores were used in the coreflood experiments. The concentration of the chelates used was 0.6M at pH values of 11 and 4. The coreflood experiments were run at a flow rate of 5 cm 3 /min and 300 o F.Coreflood experiments showed that at high pH values (pH =11) GLDA, HEDTA, and EDTA were almost the same in increasing the permeability of both Berea and Bandera sandstone cores. GLDA, HEDTA, and EDTA were compatible with Bandera sandstone cores. The weight loss from the core was highest in case of HEDTA and lowest in case of GLDA at pH 11. At pH 4, 0.6M-GLDA performed better than 0.6M HEDTA in the coreflood experiments. The permeability ratio (final/initial) for Bandera sandstone cores was 2 in the case of GLDA and 1.2 in the case of HEDTA at pH of 4, and 300 o F. At pH 11, HEDTA, EDTA, and GLDA almost were the same in enhancing the permeability of the Bandera sandstone cores. At pH value of 4, GLDA gave the best results in Berea and Bandera sandstone cores.

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Advanced Sandstone-Acidizing Designs With Improved Radial Models

Cited by 40 publications

References 17 publications

Acidizing Sandstone Formations Using a Sandstone Acid System For High Temperatures

Acidizing Sandstone Formations Using a Sandstone Acid System For High Temperatures

High-pH Clay Instability Rating

Novel Environmentally Friendly Fluids to Remove Carbonate Minerals from Deep Sandstone Formations

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