drilling fluid contamination test

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  1 | Page   1.0 ABSTRACT This experiment conducted to study the effect of contamination of Gypsum (CaSO 4    –  2H 2 O) to th e density, Plastic Viscosity (μ p ) and Yield Point (Y p ) of water based mud. Gypsum is one of the salts that commonly encountered during drilling, completion or work over operations. The experiment started by preparing 200ml based mud in a Beaker A and Beaker B and the drilling fluid initially tested for weight, PV and Yp by using viscometer. Drilling fluid initially tested for weight, PV and Yp by using viscometer. After the values were recorded, about 5g of gypsum were added in the beaker that contains water based mud. The mud containing gypsum is stirred for 3 minutes. The values of viscosity, PV, Yp, density and pH value are recorded. The experiment was repeated by adding 10, 15 and 20 grams of gypsum into the water based mud. Basically, the viscosity, pH value, density, yield point and the mud weight is increasing as the amount of gypsum is increase while for plastic viscosity; the value is decreasing as the gypsum is increase. 2.0 INTRODUCTION The drilling fluid system, commonly known as the “mud system” is the single component of the well-construction process that remains in contact with the wellbore throughout the entire drilling operation. Drilling fluid systems are designed and formulated to perform efficiently under expected wellbore conditions. Advances in drilling fluid technology have made it possible to implement a cost-effective, fit for purpose system for each interval in the well-construction process.   Drilling fluid can be divided by three types which are freshwater systems, saltwater systems, oil- or synthetic-based systems p neumatic (air, mist, foam, gas) “fluid” systems . The functions of drilling fluid in drilling operation are to clean the hole by transporting drilled cuttings to the surface, where they can be mechanically removed from the fluid before it is recirculated down hole, to balance or overcome formation pressures in the wellbore to minimize the risk of well-control issues and to support and stabilize the walls of the wellbore until casing can be set and cemented or open hole-completion equipment can be installed. Besides, drilling fluid also act to prevent or minimize damage to the producing formations, cool and lubricate the drill string and bit, transmits hydraulic horsepower to the bit and allow information about the producing formations to be retrieved through cuttings analysis, logging-while-drilling data, and wire line logs.  2 | Page    A mud is said to be contaminated when a foreign material enters the mud system and causes undesirable changes in mud properties, such as density, viscosity, and filtration. Generally, water-based mud systems are the most susceptible to contamination. Mud contamination can result from overtreatment of the mud system with additives or from material entering the mud during drilling. The most common contaminants to water-based mud systems are solids which are being added, drilled, active or inert, gypsum or anhydrite, cement or lime, makeup water, soluble bicarbonates and carbonates, soluble sulfides and salt or salt water flow. The calcium ion is a major contaminant to freshwater-based sodium-clay treated mud systems. The calcium ion tends to replace the sodium ions on the clay surface through a base exchange, thus causing undesirable changes in mud properties such as rheology and filtration. It also causes added thinners to the mud system to become ineffective. The treatment depends on the source of the calcium ion. For example, sodium carbonate (soda ash) is used if the source is gypsum or anhydrite. Sodium bicarbonate is the preferred treatment if the calcium ion is from lime or cement. If treatment becomes economically unacceptable, break over to a mud system, such as gypsum mud or lime mud, that can tolerate the contaminant. One of the sources of calcium is gypsum. In this experiment, gypsum is used as contaminator that mixes with water based-mud. Gypsum is ground Calcium Sulfate Dihydrate. It is typically act as an inexpensive source of calcium and alkalinity in gyp-based drilling muds. It can raised the pH level. Its solubility will increased at higher chloride levels. In water-based systems, it can treated trona water and CO 2  contamination. Gypsum is a very soft sulfate mineral composed of  calcium sulfate dihydrate, with the chemical formula CaSO 4 ·2H 2 O. It can be used as afertilizer, is the main constituent in many forms of  plaster and is widely mined. A very fine-grained white or lightly tinted variety of gypsum, calledalabaster, has been used for sculpture.  3.0 OBJECTIVES This experiment is to study the effect of contamination of Gypsum (CaSO4- 2H2O) to to the density, Plastic Viscosity (μ p ) and Yield Point (Y p ) of water based mud.    3 | Page   4.0 THEORY Gypsum occurs in nature as flattened and often twinned crystals, and transparent, cleavable masses called selenite. Selenite contains no significant selenium. Gypsum is a common mineral, with thick and extensive evaporite beds in association with sedimentary rocks.  Gypsum is used in gypsum or lignosulfonate or polymer muds as a source of calcium ions for inhibition and to convert bentonite to the calcium ion form. This avoids problems that might otherwise occurs when anhydrite ids drilled. It can also be used as an economical treatment for carbonate contamination in high pH muds with reaction: CaSO 4  + CO 32-     CaCO 3  + SO 42- Gypsum is deposited from lake and sea water, as well as in hot springs, from volcanic vapors, and sulfate solutions in veins. Hydrothermal anhydrite in veins is commonly hydrated to gypsum by groundwater in near-surface exposures. It is often associated with the minerals halite and sulfur. Pure gypsum is white, but other substances found as impurities may give a wide range of colours to local deposits. Because gypsum dissolves over time in water, gypsum is rarely found in the form of sand. In order to conducted the experiment, the properties that be measured surely known in term of theory which means, what the relation between the properties and the mud. Yield Point (yp) is one of parameters that be measured. Basically, it is resistance of initial flow of fluid or the stress required in order to move the fluid. The parameter usually referred to the ability of drilling mud where act as to carry cuttings to surface. Plastic Viscosity (PV) is referred to the resistance of fluid to flow. It can be measured by using viscometer. The unit of PV is Centi- Poise (CP) while for Yp is lb/100 ft 2 . Plastic Viscosity (PV) = viscosity at 600 rpm  –  viscosity at 300 rpm Yield Point (Yp) = viscosity at 300 rpm  –  PV  Apparent Viscosity = Viscosity at 600 rpm /2  4 | Page   5.0 APPARATUS  To test for density 1) Lid and Cup 4) Rider 2) Level bubble 5) Counterweight 3) Graduated arm Figure 5.1 Mud Balance To test for pH value Figure 5.2 pH meter


Jul 23, 2017

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Jul 23, 2017
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