The Use of Galena As Weighting Material in Drilling Mud
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Journal of Scientific Research & Reports 7(6): 455-465, 2015; Article no.JSRR.2015.227 ISSN: 2320-0227 SCIENCEDOMAIN international www.sciencedomain.org The Use of Galena as Weighting Material in Drilling Mud U. Akpabio Julius1*, I. Akpanika Offiong1 and O. Etim Idorenyin1 1Department of Chemical and Petroleum Engineering, University of Uyo, Nigeria. Authors’ contributions This work was carried out in collaboration between all authors. Authors UJA and IAO designed the study, wrote the protocol, and wrote the first draft of the manuscript. Author OEI managed the literature searches, analyses of the study and managed the experimental process. All authors read and approved the final manuscript. Article Information DOI: 10.9734/JSRR/2015/15095 Editor(s): (1) Shahid Naseem, Department of Geology, University of Karachi, Pakistan. Reviewers: (1) Anonymous, Universiti Sains Malaysia, Malaysia. (2) Anonymous, Southwest Petroleum University, China. Complete Peer review History: http://www.sciencedomain.org/review-history.php?iid=1130&id=22&aid=9516 Received 5th November 2014 Original Research Article Accepted 16th February 2015 Published 30th May 2015 ABSTRACT A successful oil well drilling depends largely on a good mud Program. During drilling, mud provides sufficient hydrostatic pressure, removes drill cuttings and cools drill bits. Mud additives are always required to provide sufficient hydrostatic pressure to ensure borehole stability. Barium Sulphate (BaSO4) also known as barite is the prevalent weighting material but there is need to develop local materials to augment the use of Barite. This study was aimed at assessing the suitability of galena, a lead sulfide (PbS), as an alternative weighting material in drilling fluids. Two mud samples A and B were prepared which comprised fresh water, caustic soda, bentonite and weighting material. The weighting materials were added to the mud separately to form the required mud weight ranges between 9.0 ppg and 15.0 ppg. Sample A was water-based mud with commercial barite while Sample B was water-based mud with local galena. These samples were analyzed and the density, rheological properties and solid contents were investigated. At 9.0 ppg, the yield point of galena was 20.0 lb/100ft2 and barite 22.0 lb/100ft2 while the 10 second gel strength of galena was 5.0 lb/100ft2 and 8.0 lb/100ft2 for barite. Similarly, little difference was observed in plastic and apparent viscosities. At 9.0 ppg, the plastic and apparent viscosities of galena was 13.0 cp and 23.0 cp while barite was 10.0 cp and 20.0 cp. _____________________________________________________________________________________________________ *Corresponding author: Email: [email protected]; Julius et al.; JSRR, 7(6): 455-465, 2015; Article no.JSRR.2015.227 The result show that galena mud sample gave a little higher yield point and gel strength than barite mud sample. Therefore, galena has the potential to be used as weighting material in drilling mud in place of Barite thereby enhancing the local content initiative of the government. When Galena is sourced locally and used it will reduce overall mud and drilling costs. Keywords: Barite; Galena; drilling mud; weighting material; hydrostatic pressure. SYMBOLS / NOMENCLATURE API - American Petroleum Institute AV - Apparent Viscosity BaSO4 - Barium Sulphate cc - Cubic Centimeter cp - Centipoises FeCO3 - Siderite Fe2O3 - Hematite Ib - Pounds Ib/gal - Pound Per Gallon Ib/100ft2 - Pound Per hundred Square Foot PbS - Lead sulphate PCF - Pound Cubic Foot pH - Hydrogen Concentration ion ppg - Pounds Per Gallon PV - Plastic Viscosity ROP - Rate of Penetration rpm - Revolution per Minute µm - Micrometer μP - Plastic Viscosity V-G - Viscosity – Gel Yb - Yield Point Ɵ600 - Torque reading dial at 600 rpm Ɵ300 - Torque reading dial at 300 rpm YP - Yield Point 1. INTRODUCTION are environmentally friendly if the drilling fluid is to be disposed [3]. Weighting materials increase Expected increase in drilling activities, has mud density as well as penetration rate during necessitated the search for alternative sources of drilling [4]. When there is reduction in rig time drilling mud additives so as to minimize or stop due to fast penetration rate the overall drilling the importation of weighting materials such as cost is reduced because the target is reached barite. There are many local materials which earlier. A locally obtained weighting material that could be investigated to know their suitability for can be used in place of barite would be a new use as weighting material [1]. This research was innovation in the industry. carried out on one of such weighting materials galena which is available in the lower Benue The main objective of the research is to examine trough in Ebonyi state. Drilling mud formulation the properties of a locally sourced material to comprises of water, bentonite and weighting substitute barite in drilling fluids. Galena is a lead materials. ore (lead sulfide (PbS)) which is found in Ameri and Ameka in the lower Benue-Abakaliki trough The drilling mud is usually formulated to have in Ebonyi state in Nigeria (Fig. 1) [5]; the adequate hydrostatic pressure, normally in the rheological properties are being examined and range of 250 psi to 450 psi higher than the compared with that of barite. Just as oyster sea formation pressure [2]. Imbalance between the shell, (which is locally available) can be used as hydrostatic pressure and the formation pressure lost circulation material, the mineral Galena is may cause influx of formation fluid which may being investigated to know its potential to be result in a kick and eventually a blowout. Barites used as a weighting material in drilling mud [6]. 456 Julius et al.; JSRR, 7(6): 455-465, 2015; Article no.JSRR.2015.227 1.1 Basic Properties of Galena and Barite advantages of the compound over barite was their high specific gravities. In his conclusion, Galena also called lead II sulfide is lead grey and iron-based materials were recommended for use silver in colour; it is cubic and octahedral in as a substitute for barite. shape and opaque. The hardness is 2.5 and the specific gravity is 6.7 (see Table 2). It is one of According to Saasen et al. [13] ilmenite has been the most abundant and widely distributed sulfide applied earlier as a weighting material. A higher mineral. It is found in igneous and metamorphic drilling penetration rate was reported from the rocks in medium to low-temperature use of ilmenite, because lesser colloidal solid hydrothermal. In sedimentary rocks it occurs as fractions were produced during drilling. The veins, breccia cements, isolated grains and as ilmenite used in the first two wells drilled in 1979 replacements of limestone and dolomite. The and 1980 in the North Sea, were finely ground lead element is toxic but while bound in the materials compared to the presently used crystal structure, it is safe to handle. However, ilmenite [14]. The second trial was conducted in prolonged exposure to the pulverized dust in the 1994 using a more finely ground ilmenite [15]. form of inhalation or ingestion, it is hazardous to Recently, Manganese Tetra oxide (Mn3O4) has human health. It often has common impurities been used as a weighting material for water like Ag (Silver), Cu (Copper), Fe (Iron) and Bi based drilling fluids [16]. Mn3O4 and CaCO3 were (Bismuth) [8]. The molecular mass is 239.3 prepared in the laboratory and used to conduct g/mol. experiments. Polymer starch degraded at 250ºF and cellulose were contained in the drilling fluid Barite is an inorganic compound that is white formulation to control fluid loss and rheological crystalline in appearance, insoluble in water and properties of the drilling mud. colourless. It can be heated with coke to give barium sulfide (BaS) which is soluble in water According to Symposium [17], important unlike BaSO4. It has a molar mass of 233.4 properties of drilling mud include: Density (which g/mol, and is odourless. It has a melting point of enhances borehole stability and prevents 1345ºC, boiling point of 1600ºC and refractive blowout); low viscosity and gel strength (which index of 1.64 [9]. The hardness is 3.0 and produce faster drilling and more efficient removal specific gravity is 4.5. Although, barite has a of drill cuttings). High filtrate will minimizes chip slightly higher molecular weight than galena hold-down and facilitates faster drilling [18]. (243.4 to 239.3) the molecular composition of lead in galena is higher (86.60%) [10] than According to Moore and Gatlin [19] and Eckel barium in barite (60.54%) in pure samples. [20], some of the more recognizable variables which affect penetration rate include: mud 1.2 Other Alternative Weighting Materials density, weight on bit, rotating speed and bit type [4,20]. Other factors which affect rate of A weighting material that can be sourced locally penetration are formation properties such as to substitute barite would be a good innovation in permeability, porosity and hardness, rig the drilling industry. In recent years ilmenite and efficiency and personnel efficiency. haematite have been investigated. Both minerals meet the requirements for chemical inertness The main role of the weighting materials in the and availability, but they differ from barite in drilling fluid is to increase density and ultimately specific gravity and hardness. Scharf and Watts to ensure borehole stability [21]. It also creates [11] assessed the benefits of haematite as a sufficient hydrostatic pressure in the hole and weighting material in heavy oil base systems. minimizes fluid loss by formation of thick filter This was achieved by conducting a laboratory cake on the walls of the well [22]. Increase in investigation to obtain a comparative basis density also results in increased penetration rate; between barite and haematite. Rheological however, when the density is excessive, it can properties as well as abrasiveness were studied cause differential sticking of the drill string [23].