Formate-based fluids has been successfully used in over hunders HPHT well operations since they introduced in field practice. They have many advantages when compared with conventional HPHT drilling ...and completion fluids such as: minimal formation damage, maintenance of additve properties at high temperatures, reduced hydraulic flow resistance, low potential for differential sticking, naturally lubricating, very low corrosion rates, biodegradable and pose little risk to the environment etc. Formate-based fluids can be applied during deep slim hole drilling, shale drilling, reservoir drilling, salt and gas hydrate formations drilling. The laboratory research was carried out to evaluate the rheological behavior of formate-based fluids as a function of temperature. Formate-based fluids were formulated using potassium formate brine, xanthan polymer, PAC, starch and calcium carbonate. Experimental results show that potassium formate improves the thermal stability of polymers.
Wellbore instability is one of the main problems that engineers meet during drilling. The causes of wellbore instability are often classified into either mechanical (for example, failure of the rock ...around the hole because of high stresses, low rock strength, or inappropriate drilling practice) or chemical effects which arise from damaging interaction between the rock, generally shale, and the drilling fluid. Often, field instances of instability are a result of a combination of both chemical and mechanical. This problem might cause serious complication in well and in some case can lead to expensive operational problems. The increasing demand for wellbore stability analyses during the planning stage of a field arise from economic considerations and the increasing use of deviated, extended reach and horizontal wells. This paper presents causes, indicators and diagnosing of wellbore instability as well as the wellbore stresses model.
Produced sand causes a lot of problems. From that reasons sand production must be monitored and kept within acceptable limits. Sand control problems in wells result from improper completion ...techniques or changes in reservoir properties. The idea is to provide support to the formation to prevent movement under stresses resulting from fluid flow from reservoir to well bore. That means that sand control often result with reduced well production. Control of sand production is achieved by: reducing drag forces (the cheapest and most effective method), mechanical sand bridging (screens, gravel packs) and increasing of formation strength (chemical consolidation). For open hole completions or with un-cemented slotted liners/screens sand failure will occur and must be predicted. Main problem is plugging. To combat well failures due to plugging and sand breakthrough Water-Packing or Shunt-Packing are used.
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The silicate-based drilling fluid is a low solids KCl/polymer system with the addition of soluble sodium or potassium silicate to enhance inhibition and wellbore stability. Silicate-based drilling ...fluids exhibit remarkable shale and chalk stabilizing properties, resulting in gauge hole and the formation of firm cuttings when drilling reactive shales and soft chalks. Silicates protect shales by in-situ gellation when exposed to the neutral pore fluid and precipitation, which occurs on contact with divalent ions present at the surface of the shale. Also, silicates prevent the dispersion and washouts when drilling soft chalk by reacting with the Ca super( 2+) ions present on chalk surfaces of cutting and wellbore to form a protective film. The silicate-based drilling fluid can be used during drilling hole section through shale interbeded anhydrite formations because of its superior shale stabilizing characteristics. However, drilling through the anhydrite can decrease the silicate concentration and change rheological and filtration fluid properties. So, the critical concentration of si ions should be investigated by lab tests. This paper details the mechanism of shale inhibition using silicate-based drilling fluid, and presents results of lab tests conducted to ascertain the effect of Ca super( 2+) ions on silicate level in the fluid and the fluid properties.
Historically, most underbalanced drilling (UBD) projects were undertaken to eliminate drilling problems and cost. However, recently, the reduction of formation damage has become a main focus for ...underbalanced operations. This has the greatest potential in directly increasing the profit to the operating company. Potential benefits include increasing of production rate, the ultimate recovery, and enabling accelerated production. Underbalanced technology, while still on a sharp growth curve, is finally becoming accepted as a normal method for handling the drilling and completion of wells. This paper details the benefits and limiting factors of UBD technology, underbalanced fluid system selection, and UBD techniques, as well as candidate screening and selection.
Formation Sampling and Sand Analysis Cikes, Marin; Matanovic, Davorin; Moslavac, Bojan
Sand Control in Well Construction and Operation,
2012, 20111220
Book Chapter
The starting point for any kind of sand control with respect to geomechanical approach is proper sampling and sand screen analysis. Use of bailed or produced sand samples leads to mistakes and ...problems and is the poorest kind of data that can be used in designing sand control. The representative samples are obtained by coring the whole length of the interval with adequate coring equipment. Particle size distribution is then determined through sieve and laser particle size (LPS) analysis.
LPS is used to determine the amount of fine particles that exist due the swelling and migration of bonding clays, or due the crushing during production.
Such analysis is the basis for proper design of liner openings, screens or gravel pack sizing.
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7.
Sand Control Methods Cikes, Marin; Matanovic, Davorin; Moslavac, Bojan
Sand Control in Well Construction and Operation,
2012, 20111220
Book Chapter
The main purpose of any sand control method is to hold load bearing solids in the place. It is therefore necessary to determine what is in fact produced. Some fines are always produced, and that can ...be beneficial because that helps in cleaning pore space. The other (solids between 50 and 75 percentile ranges) that are real load bearing solids can be control through reduction of drag forces, by bridging sand mechanically or by increasing formation strength. That means some kind of production rate control, selective or oriented perforating, fracturing and gravel packing, use of screens and chemical consolidation.
In this chapter aim is to concentrate on sand control tools and procedures designed to prolong well life by eliminating sand production either mechanically trapping it behind various downhole devices or chemically consolidating the unconsolidated formations prone to produce sand. Open and cased hole installations are described, involving slotted liner, standalone screen and gravel packed completions. Through tubing sand control, frac-and-pack method completion and dual zone completions are presented as well. All these completions comprise of many different tools, accessories and devices like screens, packers, seal assemblies, running tools, blank pipes, safety joints and other. They are introduced as an overview of possible tool combinations in certain occasions.
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Povijesno gledajući, tehnologija izrade kanal bušotine u uvjetima podtlaka primjenjivana je u praksi radi eliminiranja problema do kojih je dolazilo tijekom bušenja i radi smanjenja troškova. ...Posljednjih godina glavni cilj izrade kanal bušotine u uvjetima podtlaka postaje smanjenje oštećenja ležišnih stijena. Time se postiže najveće povećanje dobiti servisne kompanije. Potencijalne koristi obuhvaćaju povećanje proizvodnje, konačnog iscrpka i omogućavanje bržeg uključivanja bušotine u proizvodnju. Primjena tehnologija izrade kanal bušotine u uvjetima podtlaka i dalje je u porastu i konačno postaje prihvatljiva kao normalna metoda za izradu i opremanje bušotina. U radu se opisuju koristi i ograničenja u primjeni UBD tehnologije, izbor radnog fluida za bušenje u uvjetima podtlaka, metode UBD, provjera i izbor stijena pogodnih za primjenu ove tehnologije.
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Treating Fluid Selection Cikes, Marin; Matanovic, Davorin; Moslavac, Bojan
Sand Control in Well Construction and Operation,
2012, 20111220
Book Chapter
The major types of treating fluids that are in use in sand control are conventional linear gels, borate-crosslinked fluids, organometallic-crosslinked fluids, and aluminum phosphate-ester oil gels. ...The general behavior of these fluid systems is described. Fluid loss properties, breaking systems, and resulting formation damage are discussed and recommendations for treating fluid selection in sand control are offered.
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