Pickling Well Tubulars Using Coiled Tubing: Mathematical Modeling and Field Application

Al-Mutairi, Saleh Haif; Hill, A.D.; Nasr‐El‐Din, Hisham A.

doi:10.2118/94124-pa

Cited by 3 publications

References 16 publications

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Acid Fracturing of Gas Wells by Use of an Acid Precursor in the Form of Solid Beads: Lessons Learned From First Field Application

Nasr‐El‐Din

Al-Zahrani

Garzon

et al. 2009

SPE Production &Amp; Operations

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Summary Acid-fracturing treatments are used commonly to enhance the productivity of carbonate formations with low-permeability zones. Various forms of hydrochloric acid (HCL) are used to create deep etched fractures. However, regular HCl reacts very fast with limestone and high-temperature dolomite formations and, unless retarded, will produce a fracture with low conductivity. In addition, concentrated HCl-based acids are very corrosive to well tubulars, especially at high temperatures. To address problems associated with concentrated acids, various retarded acids were introduced. Organic acids were used also in some cases. These organic acid systems were used successfully to acid fracture several wells in a deep gas reservoir in Saudi Arabia. Field data, however, indicated that there is a need to create deeper and more-conductive fractures. To achieve this goal, it was decided to conduct a field trial with a newly developed acid system. The new acid system is an ester of an organic acid in the form of solid beads. The ester reacts with water (hydrolyzes) at bottomhole temperature and produces lactic acid, which reacts with carbonate minerals and etches the surface of the fracture. The system was examined thoroughly in the laboratory and showed promising results. The treatment was conducted in the field without encountering operational problems. After successful placement of the solid beads in the fracture, the well was shut in for 24 hours to give ample time for the ester to hydrolyze and for the generated acid to react with the formation rock. The well was allowed to flow, and samples of the fluids produced were collected to understand chemical reactions that occurred during the treatment. The treatment has resulted in a slight increase in gas production, and no significant improvement was noted over a 9-month period. Consequently, the well was matrix acidized with 28 wt% HCl and responded positively to the treatment. This paper will discuss major reactions that occurred during these treatments and how they impacted well response. Lessons learned and recommendations to improve the results of this new acid system will be given.

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Acid Fracturing of Gas Wells by Use of an Acid Precursor in the Form of Solid Beads: Lessons Learned From First Field Application

Nasr‐El‐Din

Al-Zahrani

Garzon

et al. 2009

SPE Production &Amp; Operations

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Formation Damage Caused by Pipe Dope and Its Remediation

Castineiras

Funes

Mathis

et al. 2013

SPE Production and Operations Symposium

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Historically all well strings of casing and tubing have used thread compound or "dope" to enable good connectivity, lubricity and sealability of connections. During the makeup of a connection, excess running compound or dope is squeezed out into the annular space where it can gain access to wellbore fluids and cause formation damage. The innovation of surface technologies and industrial coatings allowed the development of dope-free connections. Dope-free technology can potentially eliminate the use of all dopes in well construction.Formation damage caused by excess pipe dope is not a recently developed problem but has been overlooked in the past. This, perhaps, is because the problem for production applies to higher formation permeability than the ones studied in this paper. For relatively low-permeability formations whose pore throats are smaller compared to dope particles and therefore the latter do not penetrate the rock matrix, the problem can be mitigated by the flow of reservoir fluids The problem can also be diminished by using solvent treatments (such as toluene or xylene) to help break down and dissolve the dope compounds.The key benefit of dope-free technology is the prevention of damage to the formation caused by dope entering the formation. Additional benefits include a more reliable and robust connection and a more efficient well site assembly process. Dope-free technology guarantees better downhole performance, minimization of galling and other connection damage as well as immediate savings in the operation by removing a routine and uncontrolled manual operation on the rig floor. Reduction of heavy tubular handling and lifting operations as well as the achievement of a virtual no discharge of effluents are also important benefits.In this paper, we present the laboratory test results utilizing actual core samples. Results show the creation of a harmful dope suspension that can penetrate and damage the formation. During injection operations this can result in severe damage to the well formation (greater than 99%), while in production operations the damage depends on the reservoir permeability. Within the tested permeability range (<288 md), it is observed that the harmful compounds did not penetrate the rock matrix and, instead, it formed a filter cake that can be removed by reservoir fluid flow while in injection mode. This paper will demonstrate the benefits of using dope-free pipe connections by quantifying the negative effects of the traditional way of joining connections with dope. Various "thread dopes" are tested, showing the differing potential damage from the dope product used. Production equations using a dope-induced skin effect are also presented, showing the detrimental impact on well performance.

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"Dope-Free" Tubulars in Petroleum Well Completions

Funes¹,

Figini²,

Goretta

et al. 2013

All Days

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Dope", an inorganic compound, has been used routinely during well construction for both casing and tubing to lubricate, seal and protect against corrosion of segment-connecting threads. During the well tubular assembly a portion of the thread compound is exuded inside and outside the connection and gets access to the well fluids through the tubing and annular space. Studies presented here show that the dope forms a suspension which penetrates and damages the formation. The studies used standard fluid circulation velocities during typical completion operations. The formation damage is severe (more than 99 percent) and has been confirmed with a number of core-test experiments, presented in this work.If the well is put on injection service and in the case of workovers such as matrix stimulation treatments, the formation damage caused by pipe dope will almost guarantee operational failure. For production the issue is different and will depend on the reservoir permeability and the ability or lack thereof of the dope compound to penetrate the rock matrix or whether it will form a removable filter cake.

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Pickling Well Tubulars Using Coiled Tubing: Mathematical Modeling and Field Application

Cited by 3 publications

References 16 publications

Acid Fracturing of Gas Wells by Use of an Acid Precursor in the Form of Solid Beads: Lessons Learned From First Field Application

Acid Fracturing of Gas Wells by Use of an Acid Precursor in the Form of Solid Beads: Lessons Learned From First Field Application

Formation Damage Caused by Pipe Dope and Its Remediation

"Dope-Free" Tubulars in Petroleum Well Completions

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