Process of Matrix Acidizing

Process of Matrix venomousizingCHAPTER ONE INTRODUCTIONCHAPTER ONEINTRODUCTION1.1. PrefaceWell stimulation techniques atomic number 18 applied regularly to improve productiveness and maximize recovery from oil and gas hygienics. One of these techniques is matrix pungentizing which is probably the most extensively performed job payable to its low cost as compared to hydraulic fracturing, and its appropriateness to both production improvement and to restore original permeability in damaged wells.Acidizing treatments in general can be sort as Acid washingMatrix tartizingFracture acidizing ( or acid-fracturing)In acid washing, the purpose is simply tubular and wellbore cleaning. Treatment of the formation is not considered. Acid washing is most often Carried out to clean out scale and other materials restricting flow in the well.In fracture acidizing, acid is injected into a fracture created by a viscous wandering or the acid itself used to create the fracture. As acid progresses in the fracture, it reacts with the fracture walls, resulting in decomposition etching.Matrix acidizing which is the focal of this research, is defined as the process in which an acid is injected into the formation at pressures below the fracturing pressure of the formation so that fractures are not created. The injected fluid go forth react with the formation and dissolve some of the materials present and hence eliminate the formation damage and/or increase the permeability in the near-wellbore region.(1)The acidizing process leads to improving the maximum recovery in both sandstone and carbonate reservoirs and increasing economic reserves.In carbonate formations, matrix acidizing acts by forming conductive channels, called wormholes, by means of the formation. These wormholes penetrate beyond the near-wellbore region, or extending from perforations, as illustrated in figure (1.1). Acid-induced wormholes in carbonate carrys are similar to the holes made by earthworms undergrou nd, hence the name.(2)Often, acid will formprimarily single wormhole from limited numbers of perforations, without significant branching. That is the case when strong acids are used, such as HCl. Weaker acids, such as acetic acid, and slow down acid systems tend to create more branching of wormholes, which is preferable but only to a certain range. Retarded acid systems comprise viscosified acids (e.g., surfactant or polymer surfactant-gelled acid, emulsified acid, and foamed acid) or chemically retarded acid. The nature of wormholes created is controlled by the injection rate, temperature, and formation reaction characteristics.(2)In carbonate formations, the most frequently used acid is hydrochloric acid (HCl) which reacts with carbonates and form water (H2O), carbon dioxide (CO2), and a calcium or magnesium salt. Typical reactions in carbonates are(3)For Calcite2HCl+CaCO3 CaCl2+CO2+H2O .(1.1)and for Dolomite4HCl+CaMg(CO3)2 CaCl2 +MgCl2+2H2O+2CO2 .(1.2)Figure(1.1) CT- Scanned w ormhole structures from a core-flood experiment(4)1.2. Formation monetary valueFormation damage is a common expression denoting to the impairment of the permeability by different processes. It is an undesirable functioning and economic problem that can make out place during the different phases of oil and gas recovery from reservoirs, such as drilling , hydraulic fracturing, workover operations, and production.Formation damage indicators include permeability impairment, skin damage, and cliff of well performance. Figure (1.2) represents the common formation damage mechanisms in the order of significance.(5)Seven formation damage mechanisms were summarized by Bishop (1997).(6) These mechanism areFluidfluid incompatibilities for example emulsions formed between formation water and oil-based fumble filtrate.Rockfluid inconsistency for instance contact of possibly swelling clay by nonequilibrium water-based fluids will reduce near wellbore permeability.Solids invasion such as the in vasion of drilled solids or weighting agents .Phase /blocking for instance the invasion of water-based mud in the near wellbore region in a gas well.wettability alteration for example emulsifier adsorption altering the wettability and fluid flow features of a formation.Fines migration for instance the action of fine particulates in a rocks pore structure , as a result bridging and plugging will form in pore throats. biologic activity such as the bacterial agent that enter into the formation during drilling.1.3. General Information about Field under StudyThe Badra knowledge domain is turn up in Wasit governorate 160 Km toward southeast from Baghdad city and extends across the borders to Iran. The Badra-1 discovery well was drilled in 1979. A second appraisal well (BD-2) was drilled in late-1980s but was abandoned due to the war before reaching the planned TD and main target Mauddud reservoir.No DST, coring or production testing were done. Two appraisal wells (BD-4 and BD-5) were drilled coring and testing was in 2013. In 2011, 169 sq.km seismic 3D acquisition was done and interpreted. Figure (1.3) shows the oil field and Badra field location.Figure (1.2) Classification and order of the common formation damage mechanismsFigure (1.3)Zagros Province and Oil fields1.4. Objectives of the Present StudyThe present research aims to trope matrix acidizing process for one of the Iraqi oil wells (Carbonate formation) using Hydrochloric acid (HCl) . The purpose is to follow up the formation damage occurrence due to drilling mud and completion fluids and removal, permeability improvement, and minerals dissolution in the carbonate formation caused by the acidizing process. As well as evaluating the matrix acidizing behavior, the effect of rock heterogeneity, and to determine the optimal injection rates of the acid to create channels in these formation.A new laboratory apparatus will be designed and constructed to perform the planned experiments. The setup should reprodu ce ,as much as possible, the characteristics of the treatments conditions to investigate the effects of matrix acidizing on carbonate rocks having variable mineral composition.Extensive experiments are required to be conducted to study the validation of the operative suitability and reliability of the apparatus under a broad range of pressure, flow rate, volume pumped, and acid concentration along with different additives.The licensed StimPro software will be applied , for the first time, for matrix acidizing process for Iraqi carbonate formation.