An investigation on chemical formation damage in Iranian reservoir by focus on mineralogy role in shale swelling potential in Pabdeh and Gurpi formations.
Problems resulting from instability of Shale formations of oil and gas fields make well tight, pipes cased and also make formation eradication, mud loss, well deviation and other problems which explicitly and implicitly have effects on increasing drilling expenditure in addition, Clay minerals swelling near the wellbore make producing chemicals closed and formation destroyed. These dements have forced investigation to design appropriate fluid formulation for drilling and or transfusion in Shale layers which can minimize the damage to environment. In this fluid, preventing features of Shale be taken into account in order to minimize the costs resulted from above elements. Providing this fluid and it's remedy opposed a lot of costs. So, detecting Shale layers and active Clay minerals type in it necessary. The aim of this study is to determine and investigate Asmari , Pabdeh and Gurpi formations Clay minerals in oil field of Ahwaz and Maroon in order to predict and solve problems come from emerging special Clay components and reducing costs of drilling processes by optimizing drilling fluid conditions. Moreover, these result can be useful in investigating formation damages in water injection in increasing yield process. Damages depend on rock characteristics and one created because of Clay swelling in hole and also particle spreading which don't have swelling feature, during fluid process. Clay minerals in facing water are active (absorbing water and swelling potential) and inactive, Shales often have inactive Clay minerals such as Kaolinite, Illite and active minerals such as Montmorilonite. In this study by using two methods, wireline well log and XRD, active Clay minerals are determined.
Having clay minerals during different processes, can cause reduction in permeability of reservoir rock. this phenomena are such as Clay swelling, Clay Flocculation, formation dissolution and chemical materials absorption. Gray and Rex studied acerate Micas, Illite and Kaolinite migration. They found that migration taken place when salts density or bipolar ions density reduce or are replaced by one polar ions . The process of particle migration in porous media was studied by Muecke . He concluded that sand of non-solided rock, have large amounts of solid particles which are completely instate in porous media. He also recognized that fluid systems which are designed by that particles to prevent formation damage should involve not only Clay mineral but also ability to face other mineral materials problems and also non mineral materials. When fluid flow in monophase, and it has enough velocity to keep particles hanging, particles in formation move within porous media; unless they are kept by closed paths of porous media network. Created bridges in bottleneck maybe destroyed by pressure disorders or fluid return flows, when fluid flow is multi-phase, wettability and surface forces of rock and fluid, have an important effect on particles moves. Chang and Civan was studied practical model for chemically induced formation damage . Civan was also studied about formation damage mechanisms and their phenomenological modeling . He was also studied interpretation and correlations of clay swelling measurements .
Location of Ahwaz and Maroon field:
Ahwaz and Maroon oil fields are Along the Zagros zone and the largest oil fields in Dezful area are like sinus anticlinal with NW_SE rate which are located in Khuzestan, iran. Pabdeh formation with Shale lithology and Shale limes and Gurpi formation with combination of lime and Clay limes, are Such as most challenging formations drilled in these fields to access Bangestan and Khami group reservoirs. Asmari reservoir in Ahwaz oil field has Shale Sand rock lithology.
Clay swelling phenomenon takes place in reservoirs which reservoir rock has large amount of Clay minerals . Water phase of drilling fluid contact or injected water with formation and absorbing water by Clays and their swelling make fluid passing entries closed [3-5]. The most important Clay minerals types in premeability reduction study for almost all sand rock reservoirs are Kaolinite, Montmorillonite, Illite, chlorite and combined mineral . Clay particles swelling whose main part is Montmorillonite create instability problems of wellbore in drilling process and also there main problems in production process and EOR that are:
1) severe reduction of permeability in porous media.
2) gelatinous particles migration which cause blockage.
3) accumulation and trapping of large amounts of fluids which are shown in petrophysical logs a high percentage of water saturation. This causes the well assumed to be left, which it can produce oil without water (the known characteristics of Ahwaz Sandstone reservoir). Montmorillonite to Clay particles tend to participate in Sand formations with lower depth. Clays reactive to mentioned type don't exist in Limestone and Dolomite formations.
1. Application of well logging data:
In oil industry different logs are used. The best one to identify shale layers is radioactive logs. Atoms nucleus radioactive elements such as Potassium, Thorium and Uranium are accumulated in Clay minerals. So, it make this log on the most appropriate log to detect Shale layers. Furthermore, by using natural Gamma ray separately determine amount of each element and by table provided by Schlumberger oil company we can identify Clay minerals.
Fig 2, shown some part of Maroon 246 well log graph in which from left, in track 1 the log of natural Gamma with Gamma ray spectrum, in track 2 the log of proportion radioactive elements (Th/U, U/K, Th/K) and in track 3 separated log of radioactive elements U, Th, K have been written. The measure of each element in each section is obtained by using this logs. Also the type of Clay minerals will identified by using log Pef data and Schlumberger company charts.
2. XRD Analysis method:
X-ray diffraction method is one of the pragmatic and appropriate methods in detection and analysis of micro particle materials such as Clay minerals. Providing samples for XRD experiment has the follow steps:
A) sample washing.
C) providing liquid.
D) providing slides.
From all three slides for each sample, the slides are examined for thermal and Ethylene Glycol treatment and the third one as usual slide and by using obtained (fig 3) of each treatment, mineral forming, samples were detected. Thermal slide for 2 hours is exposed to 550 [degrees]C heat. Although because of the impact of factors such as crystalline, combination, impurities, orientation of Clay minerals and calibration analysis, quantitative measurement of the Clay quantity face problems but we can minimize the error rate by creating the same condition in providing and conductinganalysis.in addition, half quantitative methods are presented to estimate Clay minerals proportion:
[I.sub.Kaolinite/2.5] + [I.sub.Illite] + [I.sub.Montmorillonite] + [I.sub.Cholorite/2] = 100%
Discussion and Conclusion:
Among these minerals, Illite has the most quantity and is studied as main mineral in formations which is increased with increasing depth but in Gurpi middle zone it's quantity decreases.Faded emerging of montmorillonite in Maroon oil field can be considered due to marine condition or to convert a part of it to Illite. Clay minerals seldom are formed with the same structure and most of natural Clays are mixed of regular or irregular chains of Illite-montmorillonite (mixed layer). This type of mixed layer mineral is more common than others.
Having high rate of chlorite in Maroon indicates the different deposition or diagenetic conditions of formations. The middle part of Pabdeh formation and Gurpi formation in Ahwaz and Maroon oil field is composed of considerable Clay minerals such as montmorillonite which always in drilling process causes many problems. Most of Stuck drill pipes in these two zone has been reported, Which has imposed heavy and extra costs to the drilling operation. During drilling operation and with mud filtrate penetrate, and swelling of these minerals near the wellbore make production channels closed, permeability reduced and formation damaged. Knowing the condition of Clay minerals distribution in each formation provide economy in supply costs in drilling fluid and water injection, fluid treatment in each condition will be down. These reactions include using Materials preventing Shale swelling such as using oil base muds, Glycol drilling mud system and additives such as Potassium chloride (KCl) Calcium Chloride (CaCl2).
Schlumbrgers Cross Plots for clay minerals identification.
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Nima Mohammadian and Hamzeh Ghorbani
Department of Petroleum Engineering, Islamic Azad University_Omidiyeh Branch, Iran.
Received 12 October 2014
Received in revised form 26 December 2014
Accepted 1 January 2015
Available online 17 February 2015
Corresponding Author: Nima Mohammadian, IAU Omidiyeh branch, Department of petroleum engineering, Omidiyeh, Iran Tel: +989358261035; E-mail: email@example.com
Table 1: Clay minerals of maroon oilfield. Well no & Depth Illite Kaolinite Mixed Formation (m) Layer 291-Z3-As 2498 35 13 36 204-Z3-As 2500 23 30 30 224-Z3-As 2724 53 0 0 224-Z3-As 2763 29 41.5 0 291-Z4-As 2536 42 0 28 291-Z4-As 2664 69 0 0 291-Z4-As 2704 38 0 30 204-Z4-As 2680 43 0 0 204-Z4-As 2690 28 27 21 204-Z4-As 2717 38 23 29 205-Z5-As 2788 42 24 0 218-L-As 2773 59 21.5 0 Average 42.24 15 14.5 218-As-Pb 2811 77 0 0 291-Pb 2824 42 0 28 Average 59.5 0 14 267-Gu 3140 34 0 25 267-Gu 3250 30.5 0 36.5 Average 32 0 30.7 Well no & Chlorite Montmorillonite Vermiculite Formation 291-Z3-As 0 16 0 204-Z3-As 0 17 0 224-Z3-As 0 23.5 23.5 224-Z3-As 0 11.5 18 291-Z4-As 11 19 0 291-Z4-As 12 19 0 291-Z4-As 9 23 0 204-Z4-As 0 36 21 204-Z4-As 0 0 24 204-Z4-As 0 0 0 205-Z5-As 0 34 0 218-L-As 19.5 0 0 Average 4.3 16.6 7.2 218-As-Pb 23 0 0 291-Pb 9 21 0 Average 16 10.5 0 267-Gu 11 30 0 267-Gu 15 18 0 Average 13 24 0 Table 2: Clay minerals of Ahwaz oilfield. Well no Depth Illite Kaolinite Mixed & Formation (m) Layer 202-L-AS 2734 25 22 0 248-L-AS 2744 26 14.5 0 216-L-AS 2822 25 53 0 206-L-AS 2946 30 18 19 234-L-AS 2960 39 45 16 206-L-AS 2964 35.5 32.5 0 Average 30 30.8 6 202-As-Pb 2822 33 29 0 226-As-Pb 2840 27 38.3 13 216-As-Pb 2929 32 22 0 Average 31 29.7 4.3 228-T-Pb 2955 31 27 15 203-U-Pb 2888 38 28 15 211-U-Pb 2966 45 27 0 230-U-Pb 2966 19 44.2 0 250-U-Pb 2920 30 28.6 0 231-U-Pb 3055 31 12.8 0 235-U-Pb 3058 27 24 14 Average 31.6 27 6.3 228-M-Pb 3026 36 0 0 211-M-Pb 3008 33 13 0 Average 34.5 6.5 0 239-L-Pb 3120 49 0 0 234-L-Pb 3186 47 21 0 Average 48 10.5 0 226-T-Gu 3013 41 15 0 206-U-Gu 3154 36 13 19 226-U-Gu 3054 48 19 33 209-U-Gu 3057 38 21 0 Average 38 17 13 202-M-Gu 3100 28 10 0 212-M-Gu 3139 31 13 0 211-M-Gu 3202 30 3 0 223-M-Gu 3221 32 18 0 228-M-Gu 3228 42 20 0 207-M-Gu 3250 48 0 0 Well no Chlorite Montmorillonite Vermiculite & Formation 202-L-AS 10 20 23 248-L-AS 22.5 13 24 216-L-AS 0 8 14 206-L-AS 0 0 33 234-L-AS 0 0 0 206-L-AS 0 13 19 Average 5.5 9 19 202-As-Pb 7 19 0 226-As-Pb 6.7 0 15 216-As-Pb 0 19 27 Average 4.6 12.6 14 228-T-Pb 0 0 27 203-U-Pb 0 0 19 211-U-Pb 0 28 0 230-U-Pb 12.8 7 17 250-U-Pb 4.4 0 37 231-U-Pb 14.2 14 28 235-U-Pb 0 12 23 Average 4.5 8.7 25.5 228-M-Pb 8.5 22 33.5 211-M-Pb 0 24 30 Average 4.2 23 31.7 239-L-Pb 17 0 34 234-L-Pb 13 19 0 Average 15 9.5 17 226-T-Gu 12 0 32 206-U-Gu 0 0 32 226-U-Gu 0 0 0 209-U-Gu 0 0 41 Average 3 0 26.2 202-M-Gu 0 27 35 212-M-Gu 0 25 31 211-M-Gu 22 45 0 223-M-Gu 0 0 50 228-M-Gu 0 0 38 207-M-Gu 22 30 0
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|Author:||Mohammadian, Nima; Ghorbani, Hamzeh|
|Publication:||Advances in Environmental Biology|
|Date:||Mar 1, 2015|
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