Fractures and Geological Analysis of the Water Breakthrough Patterns for the Production in X Carbonate Reservoir: A Case Study from Southeast Iraq

doi:10.21203/rs.3.rs-5013737/v1

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Fractures and Geological Analysis of the Water Breakthrough Patterns for the Production in X Carbonate Reservoir: A Case Study from Southeast Iraq

https://doi.org/10.21203/rs.3.rs-5013737/v1

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This study examines fracture analysis and characterization of the X carbonate reservoir within the AG oilfield in southeast Iraq, near the Iraq-Iran border. The reservoir is categorized into zones A, B, and C, each presenting unique challenges due to its complex fractured-porous nature, limited conventional log responses, a lack of special logs, and the structural difficulties caused by the Zagros orogeny. To evaluate fracture geometry and distribution and water breakthrough patterns and their influence on reservoir quality and production efficiency, the core samples, well logs, and thin sections from 10 wells were studied. The X carbonate reservoir analysis indicated that fractures typically range from 1–25 cm in length and 0.02–0.08 mm in width, predominantly high-angle to near-vertical fractures enhancing the reservoir's permeability. The reservoir properties indicate that member B has better physical properties than member A, with higher porosity and permeability. Fracture density varies significantly across the reservoir zones, ranging between 0.7 and 9.6 fractures/meter, averaging 4.7 fractures/meter and decreasing from A to C. In zones A and B, especially in the dolomite and limestone lithologies, these fractures contribute to improved permeability and higher well productivity. For example, wells AG-7A and AG-16 maintain steady production rates of 5000 and 3000 barrels per day. However, these fractures also lead to water breakthroughs, with 57.9% of wells encountering increasing in water cuts above 10%, therefore highlighting the difficulty in managing water production. Additionally, the time for water breakthrough and the location and perforation of every well were also considered in the process of water breakthrough analysis. Furthermore, the study identified three primary mechanisms for water breakthrough: gradual edge water invasion in member B of the southern area, fractures causing water breakthrough from member B to A, and bottom water invasion in the northern area. These findings highlight fractures' essential role in encouraging oil extraction and fasting water breakthroughs, which requires effective reservoir management to maximize hydrocarbon recovery while limiting water production.

Water breakthrough. Fractures density. Fractures models. Carbonate reservoir. Core samples. Reservoir permeability

Analysis of hydrocarbon reservoir fractures involves examining both natural and induced fractures within oil reservoirs (Bratton et al. 2006). These fractures are crucial as they can greatly affect the movement and storage of hydrocarbons. To understand the impact of fractures on reservoir dynamics, it is necessary to identify these features' presence, orientation, distribution, and properties (Nelson 1985). Hydrocarbons flow more easily through fractures as pathways from the reservoir rock to the wellbore. A thorough understanding of the fracture network is essential for improving hydrocarbon recovery rates and well placement.

Precise fracture description is a necessary component of a complex reservoir model that helps predict reservoir behavior in different production scenarios. Engineers can devise improved secondary and tertiary recovery methods through fracture analysis, like hydraulic fracturing or water flooding, to augment extraction (Liew et al. 2020). Comprehending the fracture network is crucial for recognizing potential hazards such as water coning, premature gas breakthrough, and ground subsidence, thus enabling more efficient reservoir management and risk mitigation (Bitew 2008). A reservoir's economic yield can be increased, development plans can be streamlined, and operational costs can be reduced with effective fracture study and management.

One of the important oilfields in southeast Iraq is the AG oilfield, located closer to the Iraqi-Irani border. This oilfield significantly affects oil production and water cuts by creating a complex fractured-porous reservoir within the X carbonate formation. Describing and modeling fractures in this carbonate formation is particularly difficult as a result of limited conventional log responses and the absence of specialized logs. The challenge is compounded by the AG oilfield structural complexity arising from tectonic activities, particularly the Zagros orogeny (Tong et al. 2023). The AG oilfield's X carbonate reservoir is categorized into three reservoir units: A, B, and C, with A and B being the primary pay zones. Understanding fracture distribution and development in these zones is critical for several reasons. First, fractures can enhance reservoir permeability and connectivity, thus improving hydrocarbon production (Rashid et al. 2021). Second, fractures can also facilitate water breakthroughs, which can lead to rising water cuts, decreased oil recovery, and higher production costs (Wang et al. 2017). Therefore, detailed fracture analysis is necessary to optimize production strategies, improve hydrocarbon recovery, and manage the challenges associated with water breakthroughs.

The objective of this study is to analyze the geological features of the X carbonate reservoir to gain a thorough understanding of the fracture network. This will be achieved by examining core samples, well logs, and thin sections and utilizing statistical methods to evaluate rock types, fracture density, and vertical fracture distribution. The study encompasses an analysis of fractures, including their geometric parameters, development models, and impact on production, as well as a geological assessment of water breakthrough, focusing on the oilfield's southern and northern regions.

2.1 Study Area

It is approximately 350 km southeast of Baghdad (the capital of Iraq) and around 175 km north of Basrah, southern Iraq. It covers a total area of 106.8 km² and is located onshore in Iraq, with accurate coordinates at around (32°.365"N) latitude and (47.306"E) longitude; the AG oilfield is composed of two domes: a saddle area between the northern and southern domes (Fig. 1) (CNOOC 2015a). The Stratigraphic section of the strata drilled in Missan oilfields from top to bottom are Neogene Bakhtiary, Paleogene X carbonate, Cretaceous Mishrif, and Shuaiba, and the X carbonate group has three lithological successions from top to bottom, namely dolomite, limestone and sandstone/shale (Fig. 2) (Al-Mamouri et al. 2022). The part of the Kirkuk embayment region on the unstable Arabian plate shelf is identified as the AG oilfield. The Arabian-Iranian plate collision made this region especially active, leading to the complex structure of the AG field (Al-Mamouri et al. 2022). The southern edge of the Zagros foreland basin is the site of the Zagros fold belt, representing the regional tectonic setting. The AG oilfield developed through the Zagros orogeny, caused by a collision of the Eurasian plates and African-Arabian in the Late Cretaceous-Early Miocene. Compressive anticline structures with an NW-SE trending long axis were created (Du et al. 2021; Dong et al. 2022a) as a result of NE-SW trending horizontal compressional stress (Xiaole et al. 2013; Jalili et al. 2020; Karami et al. 2020), and fractures and faults were well developed in this region.

The X carbonate reservoir has 2900-3200m depth; it is divided from top to bottom into A, B, and C zones based on the electrical characteristics of the wireline logs and lithological, formation thickness, marker horizons, reservoir improvement, and oil/water contact. The A and B members are the primary pay zones. The zone B has an average thickness of approximately 120m and is divided into B1, B2, B3, and B4. Zone A is divided into A1, A2, and A3 and has excellent reservoir quality, with an average thickness of around 70m and well-developed fractures (Tong et al. 2023). They are defined as low-medium and medium-high porosity-permeability reservoirs, respectively (Sun et al. 2020). Secondary porosity created by dissolution is popular in the reservoir unit, including moldic pores, intergranular burrows and pores, which form fracture-pore reservoirs. Pre-geological studies on the AG structure indicate that two different kinds of forces resulted from the folding movement, which caused tangential deformation as a longitudinal shape. The first kind focused tension forces on the upper part of the structure, while the second indicated compression forces on the lower portions of the structure (Al-Mamouri et al. 2022). The anticline axis displayed little intensity, and the limbs were affected by high deformation (Al-Saad 2010).

2.2 Data and techniques used

Data used in this study include core sample descriptions of old wells distributed through the oilfield, conventional well logs data, water breakthrough analysis data, thin sections of AGCS-24, and the locations of fractures labeled on the wells and well test data. The study also mentions using dip logging for the areal distribution of fractures. For the geological analysis of the water breakthrough, the study considered the time for the water breakthrough, the location and perforation of each well, and the shale thickness between members B and C.

2.3 Fractures Analysis

Fractures significantly influence the production and water breakthrough of the X carbonate group in the AG oilfield. There are two typical examples, AG-7A and AG-16 (Fig. 3). The perforation section at AG-7A is in the thin oil zone of member A, but it has stable production of about 5000 bbl/d for many years, and fractures also caused the water breakthrough on AG-7. For AG-16, the perforation section is 9m, and the producing oil thickness is 1.9m. It has also had stable production of nearly 3000 bbl/d for many years (CNOOC 2015a). The fractures developed highly in these two wells, as seen from cores and well tests. The fractures may enhance the productivity of these wells. So, based on this phenomenon, we researched fractures to determine the distribution and development degree of fractures in the AG oilfield (CNOOC 2015a).

Core sample observation, thin sections, ERMI, and well-test interpretation can identify fractures. Fracture geometry parameters have been described according to the fracture description of the cores of 10 old wells and thin sections of AGCS-24 integrated with well logs. Then, the locations of the fractures were labeled on the wells (Fig. 4). Based on the statistics of the rock types with fractures and fracture types, and combined with the fracture density distribution, the vertical distribution law of fracture was summarized. The areal distribution of fractures was obtained based on the genesis mechanism of fractures in the AG oilfield and the fracture density distribution. As of November 31st, 2014, 32 wells in the AG oilfield, 12 wells with cores, and all of these wells developed fractures.

The development of fractures, which locally increase reservoir permeability, often determines the characteristics of high-production wells (Zeng et al. 2022). Based on data obtained from core characteristics testing and well logging estimation, fractures have the potential to improve reservoir permeability, well productivity, and reservoir heterogeneity. However, they may also increase unwanted water production, which would complicate reservoir management and greatly affect the water breakthroughs of oil wells.

2.4 Reservoir Properties Analysis

The distribution principles of the reservoir were finally summarized by analyzing formation characteristics, sedimentary characteristics, reservoir space types, reservoir physical characteristics, and reservoir heterogeneity.

2.5 Geological Analysis on Water Breakthrough Patterns

Through the development of the AG oilfield, the water cut rate is increasing, and most wells are water breakthroughs. As of November 30th, 2014, the composite water cut of the AG oilfield is 16.0% (CNOOC 2015a). Detecting the geological reason for the water breakthrough is a pressing matter for the AG oilfield. A detailed analysis of reservoir properties, connectivity, and fracture distribution, related to the dynamic analysis of production wells, was conducted to ensure the geological reason for water breakthrough in the AG oilfield. Additionally, the time for water breakthrough and the location and perforation of every well were also considered in the water breakthrough analysis process.

3.1 Fractures Characteristics Analysis

3.1.1 Fracture geometry parameters

The fracture geometry parameters and types of fractures were described in the AG oilfield, and the data was mainly from the core’s descriptions of the old wells, in addition to the thin sections of AGCS-24. Figures (4) shows the fracture distribution on the cored wells. The fractures are generally 1-25cm long and 0.02-0.08mm wide, which can be classified as intra-layer micro-fracture (Fig. 5). Statistics data of cored wells, lithology, and well logging analysis of wells in zones A and B of the X carbonate reservoir in AG oilfield show that the types of fractures in the region are mainly high-angle to near-vertical fractures, significantly contributing to the reservoir quality development (CNOOC 2015a) as shown in Table 1.

Table 1

Statistics of the fracture types from the core description of well AGCS-24 in AG oilfield
Well	Depth (m)	Statistics (%)	Fracture Types
AGCS-24	2992.06	64	Vertical fracture
		57	Unknown-directional fracture
		18	Multi-directional fracture
		6	Horizontal fracture
	2974.54	44	Vertical fracture
		39	Unknown-directional fracture
		13	Multi-directional fracture
		4	Horizontal fracture

3.1.2 Fracture development models

3.1.2.1 Vertical Characteristics

For example, Table 2 shows the fracture density varies from 0.7–9.6 f/m, averaging 4.7 f/m. The fracture density in AG-1 indicates that the fracture density decreases from member A to member C (Fig. 6). According to the statistics of the rock types in the fracture area, the fractures mainly develop in the dolomite and limestone, as demonstrated in Table 3. Based on the above data and analysis, we summarize widespread and vertical distribution patterns of structural fractures. The development degree of fracture decreases from member A to C gradually; semi-filled or non-filled fractures are common and, therefore, conducive significantly to the development of the reservoir quality (Fig. 7a) (CNOOC 2015a).

Table 2

Fracture density values derived from the cored wells in AG oilfield
Wells	Fracture Density (f/m)
AG-2	3.8
AG-4	3.0
AG-1	2.0
AG-13	9.6
AG-7	5.2
AG-9	0.7
AG-3	5.7
AG-10	4.8
AG-14	2.9
AG-101	9.1

Table 3

Statistics of lithology with fractures from the core description of well AGCS-24 in AG oilfield
Well	Depth (m)	Statistics (%)	Lithology Types
AGCS-24	2992.06	71	Dolomite
		63	Limestone
		5	Sandstone
		6	Shale
	2974.54	49	Dolomite
		44	Limestone
		3	Sandstone
		4	Shale

3.1.2.2 Areal distribution

According to the statistics of dip logging of AG-2, the azimuth and strike of the fractures can be obtained. The azimuth of fractures in well AG-2 is NNE, and the strike of fractures is NNW (Fig. 8). As a result, the small-scale, locally forming fractures parallel to the structure axis filled to the highest point are hardly useful for developing reservoir quality.

The Zagros orogenic movement extruded the X carbonate group in the AG oilfield after the layer was deposited (Fig. 9). Mechanically, fractures of the X carbonate group in the AG oilfield are mainly tension fractures and controlled by tension stress (CNOOC 2015a). The more severe the folding is, the more developed the fractures are. So, the anticline axis and structural transfer zones are the favorable regions for developing fractures, and we draw the possible distribution of fractures in the AG oilfield based on 10 wells' fracture density and fracture development mechanism (Fig. 7b).

3.2 Fractures influence field production performance

The core samples and well tests indicate improved permeability in fractured zones in the X carbonate reservoir of the AG oilfield, especially in zone A dolomite (Fig. 10). In the wells with high fracture developed, the permeability becomes very good (Figs. 11; 12) and Table 4. On the other hand, zone B consists of limestones interbedded with sandstones and is a medium-high permeability reservoir representing the main target of perforation and the key to improvement. The wells with high fracture development show high initial productivity (Fig. 13). The initial productivity of the AG-16 well is about 1800 barrels per day per meter, and the initial productivities of AG-7A and AG101 are above 500 barrels per day per meter. In addition, fractures can affect water breakthroughs in oilfield production, especially in wells with high fracture density (CNOOC 2015a).

Table 4

Comparison of the permeability values from the core and well test data
Formation Members	Wells	Permeability (mD)		Remarks
Formation Members	Wells	Core	Well Test	Remarks
A	AG-6	2.3	2560	high fracture
	AG-7	0.86	1700	high fracture
	AG-10	24.5	103	high fracture
	AG-101	12.97	39.6	high fracture
	AG-16		133	high fracture
	AG-11	82.1	123
	AG-9	6.1	185
	AG-1	6	1850
B	AG-6	33.1	2078	high fracture
	AG-3	35.6	1656	high fracture
	AG-101	75	1267	high fracture
	AG-7	48	980	high fracture
	AG-10	49	103	high fracture
	AG-4	22	50
	AG-9	21.3	23.5
	AG-11	180	123
	AG-1	145	226

3.3 Reservoir Analysis

The reservoir shows economically significant oil productivity, according to the results of the reservoir analysis. The physical characteristics of the member B are better than member A. Member B is classified as a medium-high permeability and medium porosity reservoir, while Member A is classified as a poor-medium permeability and poor porosity reservoir. The permeability of the B4 interval in member B is better compared with other intervals for the presence of sandstone beds, as demonstrated in Table 5.

Table 5

Petrophysical properties of X carbonate reservoir in members (A and B) in AG oilfield
Layers	Average Porosity (%)	Average Permeability (mD)	Reservoir Type
A1	8.93	15.34	Poor porosity, medium permeability
A2	6.87	16.97	Poor porosity, medium permeability
A3	9.67	4.48	Poor porosity, poor permeability
A	8.72	10.61	Poor porosity, poor-medium permeability
B1	13.62	30.49	Medium porosity, medium permeability
B2	18.53	122.15	Medium porosity, high permeability
B3	14.76	14.88	Medium porosity, medium permeability
B4	17.96	494.49	Medium porosity, high permeability
B	16.78	268.5	Medium porosity, medium-high permeability

3.4 Water Breakthrough Analysis

The water breakthroughs can lead to increased water cuts, reduced hydrocarbon production, and higher operational costs. There are 11 wells with water cut over 10%, about 57.9% of the total count of wells; and 2 wells with water cut between 2%-10%, about 10.5% of the total count of wells; and 6 wells are water-free, about 31.6% of the total count of wells. Through comprehensive analysis of reservoir properties, connectivity, and fracture distribution, combined with the dynamic analysis of production wells, three models of water breakthrough for AG oilfield have been summarized as follows.

3.4.1 Edge water gradually invaded the member B in the southern region

The southern region of the AG oilfield is the main structure area, which is a laminated edge water reservoir as a whole controlled by structure (Fig. 14). For the southern region of the AG oilfield, the shale between members B and C averages 15.2m (Fig. 15) which will act as baffles or barrier, this indicates that the water of member C is difficult to go to member B directly.

In addition, the reservoirs in member B are thick and permeable, especially in the unit of B4. Besides, the continuity of the reservoirs is good. The NTG of member B is near 60%, and B4 is 76%, as demonstrated in Table 6. Moreover, the thickness of a single reservoir for member B is thick. Figures (16) shows that about 15% of reservoirs are thicker than 6m, and more than half are over 2m. The average porosity of reservoirs in member B is 16.78%. The average permeability of reservoirs in member B is 268.5mD, and that of B4 is about 500mD, as shown in Table 5. Hence, this reservoir characteristic allows edge water to invade member B gradually. Figures (17 and 18) illustrate that the wells at the low structure or with the perforation section close to OWC are more easily invaded than others. So, based on the above comprehensive analysis, it can be inferred that the edge water invasion is the main reason for the water of member B in the southern region (Fig. 14) (CNOOC 2015a).

Table 6

The Net to Gross of X carbonate reservoir layers in AG oilfield
Layers	Net/Gross (%)
A1	38.28
A2	38.62
A3	47.56
A	42.00
B1	37.54
B2	50.73
B3	43.02
B4	76.46
B	56.98

3.4.2. Water breakthrough for member A in the southern region caused by the edge water from member B

Member A is a big pure oil reservoir without water-oil contact and is far from OWC vertically. Water breakthrough was found in 3 of the five wells producing member A. The reason for the water breakthrough at AGCS-24 may be poor cementing quality. For the other two wells, AG-7A and AG-101, with high fractures, the water for member A was attributed to fractures connecting the two members, whereas member B had been flooded earlier (CNOOC 2015a). Namely, the edge water in member B goes to member A by fractures (Fig. 19). Besides, the shale thickness between members A and B is thin; the average thickness is 1.5m (Fig. 20). Hence, the reservoir of members A and B may be connective. Therefore, there is an explanation that the water breakthrough in member A was likely caused by the edge water through member B on AG-7A and AG-101 (Fig. 12).

3.4.3 Water came from the bottom water in the northern region

There are two wells, AG-2 and AG-4, in the northern region; both are water breakthroughs. The producing zones of AG-2 and AG-4 are close to the bottom water. As AG-4, it is about 10m from the perforation bottom to the water top. Moreover, these two wells are characterized by high fractures and good permeability in member B (Fig. 21). Fracture density is 3 and 3.8 f/m on AG-2 and AG-4. Thus, it can be determined that the water comes mostly from the bottom (Fig. 22) (CNOOC 2015a).

4.1 Fracture geometry and development

The fractures become communication paths among dissolved pores, enhancing connectivity within the reservoir. The study highlights the presence of intra-layer micro-fractures in the AG oilfield, which play a crucial role in reservoir connectivity. The predominantly vertical orientation of these fractures is beneficial for reservoir development.

Gradually, the development degree of fracture density decreases from member A to C, indicating a decline in the development degree; semi-filled or non-filled fractures are commonly conducive significantly to reservoir quality development. The orientation and distribution of fractures suggest they are controlled by tension stress, with favorable regions for fracture development being the anticline axis and structural transfer zones.

4.2 Fracture impact on reservoir quality

The high initial productivity in wells with high fracture development influences reservoir quality by enhancing permeability and facilitating fluid flow. However, the degree of fracture development varies across reservoir units, impacting reservoir performance and how fractures can lead to water breakthroughs.

4.3 Reservoir analysis

The analysis shows variations in petrophysical properties and the economic importance of the oil productivity in the reservoir between different members of the X carbonate formation. Member B displays better reservoir characteristics than Member A, with higher porosity and permeability.

4.4 Water breakthrough analysis

The analysis connects water breakthroughs to structural factors such as edge water invasion, poor cementing quality, and connectivity between members A and B because of fractures. The study highlights the role of fractures in facilitating water entry into the reservoir and the impact of water breakthroughs on-field production, particularly in areas with high fracture density, including increased water cuts and reduced hydrocarbon production. Understanding the mechanisms of water breakthroughs is essential for effective reservoir management.

The study identifies three potential mechanisms for water breakthrough in the AG oilfield: edge water invasion of member B, water breakthrough for member A caused by the edge water from member B, and bottom water invasion. Fractures are a main factor in facilitating water movement and accelerating water breakthroughs in certain areas.

This study has provided a detailed fractures analysis and reservoir characterization of the complex fractured-porous X carbonate reservoir in the AG oilfield, highlighting the important role of fractures in hydrocarbon production and water breakthrough patterns. By studying core samples, well logs, thin sections, statistical methods of rock types with fractures, fracture density distribution, and vertical distribution law of fracture, we have identified the characteristics and distribution of fractures across the reservoir zones. Our results indicate that fractures significantly influence reservoir permeability and connectivity, enhancing oil production and facilitating water breakthroughs, particularly in highly fractured zones.

The X carbonate reservoir's fractures range from 1 to 25 cm in length and 0.02 to 0.08 mm in width. Fracture density varies widely across reservoir zones, averaging 4.7 fractures per meter, confirming the reservoir's heterogeneity. Vertically, the development degree of fracture is downward from member A to C. Usually; fracture may develop along the AG oilfield's anticline axis and structural transfer zones. The X carbonate reservoir is categorized into zones A, B, and C, with zones A and B being the primary pay zones. Member B has medium-high permeability and medium porosity, which are better physical properties than member A, according to reservoir properties, making it more possible to invade by edge water. Intra-layer micro-fractures are quite developed through the reservoir and are mainly comprised of high-angle to near-vertical fractures with small openings in the AG oilfield, significantly enhancing the reservoir's permeability and well productivity in a direction mainly NNE-SSW and NNW-SSE. However, they can also facilitate unwanted water invasion.

In dolomite and limestone lithologies within zones A and B, these fractures have increased well production rates, with some wells, such as AG-7A, producing up to 5000 barrels per day and the AG-16 reaching 3000 barrels per day. The original oil-in-place estimation of the wells is 1613.24MMSTB, and recoverable reserves are 567.8MMSTB, displaying a good improvement impact. However, these fractures also present challenges in water production, with 57.9% of wells encountering water cuts over 10%.

Three types of main mechanisms for water breakthrough have been identified in the AG oilfield: gradual edge water invasion in member B of the southern area due to its good reservoir characteristics, fractures causing water breakthrough from member B to A, and in the northern region, the water invasion from the bottom water through fractures in AG-2 and AG-4 with high permeability near the water contact. The data indicates that fractures improve oil production and rapid water breakthroughs, especially in zones A and B. These findings highlight that understanding the fracture distribution and development in the AG oilfield is important for improving reservoir management strategies to optimize hydrocarbon recovery, minimize water production, and reduce production costs. Effective reservoir management strategies should aim to control water production through methods such as selective well completions, water shut-off techniques, and careful monitoring of the fracture networks.

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Conflict of interest

The authors want to declare that there is no conflict of interest to disclose or personal relationships that could have appeared to influence the work reported in this research.

Ethical approval

This article contains no studies performed by authors with human participants or animals.

Funding

No funding was received for this study.

Author Contribution

H. A. Chafeet: Conceptualization, Methodology, Validation, Formal analysis, Investigation, prepared figures and tables, Data curation, writing main manuscript text, Visualization, Project administration, A. M. Al-Abadi: Supervision, Formal analysis, Conceptualization, Methodology, Writing – review, and editing the manuscript, R. Z. Homod: Validation, Supervision, Visualization, Writing, review, and editing the manuscript, and A. M. Handhal: Data curation, writing, review, and editing the manuscript.

Data Availability Statement

The corresponding author's dataset supporting this study's findings is available upon reasonable request. Interested researchers can contact the corresponding author to obtain access to the dataset.

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Fractures and Geological Analysis of the Water Breakthrough Patterns for the Production in X Carbonate Reservoir: A Case Study from Southeast Iraq

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Abstract

Figures

1 Introduction

2 Materials and Methods

2.1 Study Area

2.2 Data and techniques used

2.3 Fractures Analysis

2.4 Reservoir Properties Analysis

2.5 Geological Analysis on Water Breakthrough Patterns

3 Results

3.1 Fractures Characteristics Analysis

3.1.1 Fracture geometry parameters

3.1.2 Fracture development models

3.1.2.1 Vertical Characteristics

3.1.2.2 Areal distribution

3.2 Fractures influence field production performance

3.3 Reservoir Analysis

3.4 Water Breakthrough Analysis

3.4.1 Edge water gradually invaded the member B in the southern region

3.4.3 Water came from the bottom water in the northern region

4 Discussion

4.1 Fracture geometry and development

4.2 Fracture impact on reservoir quality

4.3 Reservoir analysis

4.4 Water breakthrough analysis

5 Conclusion

Declarations

Conflict of interest

Funding

Author Contribution

Data Availability Statement

References

Additional Declarations

Status:

Version 1