Thin-bedded carbonate reservoirs face significant challenges in characterization and development due to their thin formation thickness, strong interlayer heterogeneity, and rapid sedimentary transformation. In recent years, horizontal wells have played an increasingly important role in improving the productivity of thin-bedded carbonate reservoirs. However, building accurate geological models from horizontal well data is a major challenge for geoscientists. Using Middle East Oilfield A as a case study, this paper analyzes the specific challenges of horizontal well geomodeling and proposes a dedicated strategy for integrating horizontal well-derived constraints into the geological modeling workflow. To address the challenges of structural modeling constrained by horizontal well data, this study proposes three methodologies: stratigraphic layer iteration, virtual control point generation, and localized grid refinement. These techniques collectively enable the construction of a higher-fidelity structural framework that rigorously honors hard well data constraints while incorporating geological plausibility. To address the challenges posed by the spatial configuration of vertical and horizontal wells and the dominant trajectory patterns of horizontal wells, this study introduces two complementary approaches: the exclusion of horizontal well section data (relying solely on vertical wells) and the selective extraction of representative horizontal well section data for variogram derivation. These methods collectively enable the construction of a geologically realistic reservoir model that accurately captures the spatial distribution of reservoir properties. These methodologies not only effectively leverage the rich geological information from horizontal wells but also mitigate spatial clustering effects inherent to such data. Validation through development well production data confirms robust performance, providing transferable insights for reservoir characterization in analogous fields worldwide.

Pressure gradient method is based on the principle of connectedness, using formation pressure test data to character pressure gradient curves of reservoir fluids and distinguish oil water contact. The greatest advantage of this method is Intuitive identification of oil and water contact depth. It provides basis for fine reservoir description and progressive exploration and development. According to the data of single well test, the regional water pressure curve is fitted. The difference between the hydrostatic pressure curve and the hydrostatic pressure curve is defined as the overburden pressure. The depth of test point and test pressure, formation water density and crude oil density are established to calculate the depth of oil-water contact. Well Che 47 Block, because of many times of vertical volcanic cycle, complex lithology and lithofacies, and strong heterogeneity of secondary reservoirs, multiple lithologic shielding bodies can be identified. By using the pressure gradient method and combining the reservoir geological characteristics of the industrial area, it is revealed that at least 3 relatively independent reservoir units in the Well Che 47 Block, and the corresponding depth of oil-water contact is −2786 m, −2848 m and −2912 m respectively. According to the relationship between the depth of the oil and water contact and the position of the test point, it is conservative to predict that the lowest oil layer is at least 200 m of the oil column height, and the prospect of rolling is good. The application of the pressure gradient method to identify the oil-water interface in complex reservoirs is more in line with the actual underground conditions. This method, combined with seismic and log data, can provide an important basis for the fine evaluation of complex volcanic reservoirs.

Marine nodular limestone reservoirs are generally developed in the Middle East, some oilfields such as Halfaya, Ahdeb, Azadegan have reserves of more than 4 billion tons and the capacity to produce more than 400 million tons. Strengthening the study on the genesis of nodular limestone reservoirs is of great significance to improve the accuracy of characterization. In this paper, the research object is the reservoir of the Lower Cretaceous Khasib Formation in Iraq A Oilfield. Based on core, thin section, logging and other basic data, this paper studies on reservoir characteristics and sedimentary diagenesis, and clarifies the genetic mechanism of nodular limestone and its control on reservoir. The results show that:（1）Nodular limestone reservoirs are developed in various carbonate rocks such as green algal bioclastic limestone, micritic bioclastic limestone and bioclastic sandy limestone. Most cores of Khasib limestone reservoirs are characterized by nodule, which can be divided into white and dark patches according to the color. The white patch reservoir is dense and oil-free, the dark patch reservoir has good physical properties and is oil-bearing.（2）The intergranular pores of bioclastic in white patches are almost completely cemented by bright calcite, while the cementation of bright calcite in dark patches is weak and intergranular pores are developed.（3）In the sedimentary discontinuous period, the form of hardground of early diagenesis is mainly divided into four stages: biological disturbance, nodule growth, nodule fusion, and exposure dissolution. It is the main controlling factor for the formation of nodular limestone reservoirs. The late diagenesis inherits and further strengthens the reservoir heterogeneity formed by early diagenesis.（4）The more mature the hardground is, the more obvious the improvement of reservoir physical properties is. Among them,the high permeability layer developed in Khasib Formation belongs to the mature hardground. After the dissolution by atmospheric water, the pore structure is further improved. The anti-compaction effect of the hardground in the late diagenetic stage preserves the high permeability channel in the mature hardground. This study clarifies the reservoir characteristics and genetic mechanism of nodular limestone reservoirs, which is of great significance to improve the characterization accuracy of nodular limestone reservoirs and formulate reasonable development（adjustment） technology policy.

The tight gas reservoirs in Dehui fault depression have deep burial, large span and pore-throat connectivity. Although the high-density well completion volume fracturing technology has achieved profitable development, there are some problems such as large difference in productivity effect after different well pressure and short stable production time. Through the analysis of the relationship between productivity and the factors such as high-quality reservoir thickness, sand laying strength, crack complexity and water lock damage of constructed well, the main controlling factors affecting the productivity of a single well are identified, and a series of fracturing technical countermeasures were formed, such as differential perforation, “three-stage” first forming fractures and then forming networks, first seam and then networking, multi-stage temporary plugging steering, and waterproof lock fracturing fluid system, etc. The field test of DS80-2 well showed that gas was seen on the second day after pressure, gas flowback rate was 3.8%, daily gas was 8.5×10~4 m~3, and the open flow rate was 19.2×10~4 m~3, which was the highest gas production and the lowest gas flowback rate in gas reservoirs with the same thickness in the same block. Compared with the designed production capacity, the production is increased by 20%,and the cost is reduced by 19%, which achieves the purpose of increasing production and controlling investment and provides technical support for realizing efficient exploration and beneficial development of tight gas reservoirs.

“Plaque” limestone is widely developed in Ahdeb, Halfaya, West Qurna, Misan and other oilfields in the Middle East. It has strong heterogeneity, complex porosity and permeability relationship, serious single-layer inrush in water injection development, and rapid rise in water cut. And other characteristics. The “Plaque” limestone cores appear as white and dark gray patches, the white patches are dense calcareous cementation, the dark gray patches are rich in oil, and the configuration of effective reservoirs and non-reservoirs The relationship is not the conventional superimposed distribution, but the effective reservoirs of bioturbation origin distributed among the white oil-free tight cements. The biggest feature of core observation is the “Plaque” feature. This kind of effective reservoir characterization is still using conventional carbonate rock characterization methods, so the characterization accuracy is insufficient in terms of effective reservoir seepage space, reservoir porosity and saturation properties, and reserves evaluation. In this paper, on the basis of thin section analysis of coring wells and petro-electricity fine calibration, using image analysis technology, logging curve fitting and other methods, a logging identification standard based on tight cements of different rock types is established. The relationship between block development content and logging parameters can be used to characterize the development content of tight patch development sections in uncored wells. It has important guiding significance for clarifying the development law and spatial distribution of cement, and provides a reliable geological basis for the fine characterization of effective reservoirs, the formulation of reasonable development plans, and the grasp of oil-water movement rules for water injection development.

The Cenomanian–Early Turonian Mishrif Formation is a great contributor to oil production in Iraq. Integrating petrographic, mineralogical, and wireline logging data from 52 wells, this study provides an improved understanding of the sequence stratigraphy, depositional evolution, and reservoir characteristics of the Mishrif Formation in the Mesopotamian Basin, south Iraq. Five types of facies associations are classified: lagoon, shoal, rudist bioherm, shallow marine, and deep marine. Such a classification allows convenient differentiation and interpretation of wireline logs. A sequence stratigraphic framework including five third-order sequences (Mhf 1 to Mhf 5) for the Mishrif Formation is established mainly using wireline logging data of close-distance wells, with the aid of cores and thin sections. Two end-member depositional evolution stages are recognized, from clinoform-like progradational shoal complexes in Mhf 1 within a shallow marine environment, to tidal channels in Mhf 2–3 within a lagoon environment. For Mhf 4–5, abrupt changes in facies associations from north to south indicate the development of an intra-shelf basin where organic-rich mudstones directly overlie the shallow marine grainstone shoals and lagoonal wackestones. Reservoir characteristics and compartmentalization are directly controlled by the sequence stratigraphic framework. Sequence boundaries are featured by wackestones and mudstones overprinted by cementation; they are regionally correlatable and work as regional barriers. Shoal complexes in Mhf 1 and tidal channels in Mhf 2–3 are the main reservoir units. Mudstones and wackestones are intra-reservoir baffles and become more frequently developed towards the south, reflecting the increasing water depth towards south. The characterization of the tidal channels, clinoform-like shoals, and intrashelf basinal deposits in the current study could benefit later development of the Mishrif Formation.

Pore space texture and its pore size distribution are critical parameters for displacement efficiency for waterflood, which have been applied in Middle East. For sandstone, pore size is a log-normal distribution usually. However, when it comes to carbonate reservoir, complex sedimentary and diagenesis yield complex pore size distributions including unimodal, bimodal and multimodal distribution. Therefore, it is not reasonable to classify different pore size distribution through statistic parameters such as mean, standard deviation, skewness and kurtosis. It is essential to propose a novel method to classify numerous pore size distribution results accurately and automatically by curve shape. This paper proposes the application of earth mover's distance (EMD) to pore size distribution, which is not mentioned before. The automatic clustering method is efficient and accurate to process massive data. Therefore, this method can prompt to systematic analysis and research of a giant scenario of reservoir injection characteristics in Middle East.

With the deepening study of carbonate oil and gas reservoir in the Middle East, it is recognized that marine carbonate reservoirs have strong heterogeneity from macro to micro, and some reservoirs even show high permeability layers or special "spotted" heterogeneity. "Patch" is named according to the shape and meaning of the morphological characteristics of rock structure, that is, "Patch" carbonate rock core is mainly represented by patches of light gray, dark brown, black and other colors. Taking the late Cretaceous Mishrif main reservoir of a oilfield in Iraq as an example, based on the core, thin section and other basic data, the study on the characteristics of effective reservoir space of carbonate reservoir is carried out, and it is clear that the causes of effective reservoir space of Mishrif carbonate reservoir include: sea level height, hydrodynamic strength and sedimentary discontinuity events in sedimentary period, including biological disturbance, hard bottom cementation The transformation of primary pores by atmospheric fresh water dissolution plays an important role in controlling the formation of effective reservoir space.

为方便准确地确定自由水界面的变化规律,提出了一种基于特征点的测井曲线对比拾取方法和基于该方法的 自由水界面确定模型及算法流程.首先以测井曲线为对象,通过分析寻找测井曲线特征点,并对比追踪井间地层,得到一系列具有相同或者相似岩石物性的数据集合.然后联合J函数和阿尔奇公式,推导相同特征点下 自由水界面海拔深度、距离 自由水界面深度与电阻率之间的理论数学模型,并同时建立了水平和倾斜两种自由水界面分布模式.在理论模型的基础上,提出了以回归方程判定系数为优化目标的算法,通过预设实验数据以及添加高斯白噪音方法验证了算法的合理性和鲁棒性,最后使用该方法确定了伊拉克生物碎屑灰岩油藏的自由水界面.研究结果表明,某一特征点下电阻率与距离自由水界面高度在双对数坐标下具有线性关系.通过理论模型可以表征自由水界面水平和倾斜情况下的分布模式.基于优化算法求解该模型的精度取决于非均质性程度及数据质量控制,当没有观察误差时,曲线完美拟合,曲线拟合的质量随观察误差的增大而降低,因此运用模型前必须做好质量控制,保证模型精度.实际应用中,可以利用降噪技术对数据进行前处理,从而提高模型精度.新方法对于分析地质现象、进行参数计算具有重要意义,还可以推广应用到测井解释、数据质量控制、沉积相分析、地质建模等方面.

‘Nodular’ limestone reservoirs are commonly developed in the Middle East carbonate reservoirs. Due to the firm heterogeneity and unclear genesis of this kind of reservoir, the accuracy of reservoir characterization and development plans were severely restricted. In this paper, the research object is the Late Cretaceous Khasib formation reservoir in A oil field in the Middle East. Based on core, thin section, logging, and other fundamental data, this paper studies sedimentation, early diagenesis, and late diagenesis, establishes diagenetic sequence and clarifies the genetic mechanism of ‘Nodular’ limestone and its control on reservoir: ① The Kh2 reservoir is deposited in highstand systems tract (HST). From bottom to top, with the increasing hydrodynamic force, planktonic foraminiferal limestone, green algal bioclastic limestone, micritic bioclastic limestone, and bioclastic sandy limestone are developed respectively; ② The hardground cementation of early diagenetic occurs in the period of sedimentary discontinuity, which is mainly divided into four stages: sedimentary discontinuity and bioturbation, nodule growth, nodule fusion, and exposure dissolution, which are the main controlling factors for the formation of ‘Nodular’ limestone; ③ The middle-late diagenesis is the inheritance of the early diagenesis, which can be divided into three stages: shallow burial, medium burial, and deep burial, further strengthening the reservoir heterogeneity; ④ The high permeability layer developed in the Khasib Formation belongs to the mature hard ground. The pore structure is further improved after the dissolution of atmospheric water. The anti-compaction effect of the hard ground in the late diagenetic stage preserves the high permeability channels in the mature hard ground.

The Kh2 segment in the Iraq A oilfield in the Middle East is an important oil and gas producing layer. It is affected by sedimentation and diagenesis, and has strong interlayer heterogeneity. The water injection development has a serious single-layer burst and the water cut rises rapidly. Based on a large number of core and thin section data, microfacies types of the Kh2 segment of Iraq A Oilfield are identified. Combined with reservoir physical property and mercury injection data, through the analysis of pore type, physical property characteristics and pore structure difference, it is considered that the Sand beach and bioclastic beach are the most favorable microfacies for the development of reservoirs in the Kh2 segment, followed by the inter-shoal microfacies. The rapid evolution of sedimentary microfacies is the main reason for the strong interlayer heterogeneity in the Kh2 segment. Due to the continuous interruption of deposition during the deposition process, nodular calcareous deposits are formed under strong cementation, and have obvious rhythmic characteristics in the sequence, which increases the complexity of the reservoir. Due to the combined action of biological disturbance and exposure and corrosion, the Kh2–1 formation developed a high-permeability layer with an average thickness of 1.1 m, dominated by inter-granular pores and pore-reduced throats, with an average permeability of 241 mD and a displacement pressure of 0.01–0.1 Mpa. The study of reservoir sedimentary and diagenetic characteristics can provide reliable geological basis for fine reservoir characterization and water injection development research of stratified system.

为精细表征碳酸盐岩储层非均质性及准确预测储层物性参数,以伊拉克地区孔隙型生物碎屑灰岩油藏为对象,地震、测井、地质、油藏、钻采等多专业资料为基础,静态和动态资料相结合,形成了一套基于水平井的三维地质建模方法.综合分析岩心、测井响应特征,建立了水平井水平段分别位于小层内及小层间穿行时的测井响应模式.通过旋回厚度方法,在水平井水平段上确定一系列层面节点,采用"地震层面约束+趋势线控制+虚拟井局部优化"方法,将直井和水平井充分耦合,建立精细三维构造模型.利用岩心、薄片、扫描电镜和测井等资料,建立目标油藏岩石类型模型.基于岩石类型模型,采用序贯高斯模拟,利用地震古地貌作为协同约束参数,建立不同岩石类型下的孔隙度和渗透率模型,并结合实钻井及生产动态进行模型验证.结果表明,岩心实测渗透率与预测值符合率高,模型预测的构造顶面深度、物性参数与实测结果吻合度高,符合精度要求,可有效指导油藏动态分析、数值模拟、剩余油预测及开发方案调整.

The Persian Gulf Basin is located at the junction of the Eurasian Plate and the Arabian Plate. It is mainly developed on the Arabian Plate and belongs to a large foreland sedimentary basin. The Persian Gulf Basin is extremely rich in oil and gas resources. As of 2012, more than 1,260 oil and gas fields have been discovered in the Persian Gulf Basin, with a total recoverable reserves of 221.58 billion tons of oil equivalent, accounting for 38

This paper proposes a new method called typical points-based well log correlation and picking up technology and provides several related application examples based on this method. The new method firstly determines representative extreme points, typical or characteristic points by analyzing the characteristics of logging curves and lithology of different wells, which are generally representative points with special geological significance, including the points with the best physical properties or tight points. (For example, the maximum flooding surface or exposed surface in a sedimentary cycle, etc.). On the basis of these characteristic points, we carry out stratigraphic correlation and tracking between wells to obtain a data set of a series of characteristic points. From the same characteristic point, all points have the same or similar petrophysical properties, and the logging curve values of these characteristic points are extracted. And then analyze the change trend, distribution characteristics and the internal relationship of the parameters of the data set of each feature point. Based on the data set obtained from the method above, we extended it to the following application areas: 1) Through mathematical theoretical models, two free water level distribution modes and their determination workflows were established, including horizontal and tilted free water levels. 2) Perform data quality analysis and control, especially logging data analysis. 3) Exploratory application in the standardization of logging curves.4) Application in dynamic performance analysis The new method is developed on the traditional stratigraphic correlation method and stratal slicing method (Zeng Hongliu, 1998) and then used for well log data extraction and analysis. It is a practical means and technique for geological analysis. The application effect shows that the it is reliable, convenient and practical.

Carbonate reservoir with high permeability is highly heterogeneous, In the process of flood development, the injected water is easily channeled along the thin layer with high permeability, which reduces the efficiency of water drive development and the ultimate recovery rate. This paper takes a carbonate reservoir developed in a high permeable layer in the Middle East Persian Gulf as an example, aimed at stable injection production mode of row well pattern for horizontal wells, from the perspective of hydrodynamics, by developing asynchronous and unstable injection production of oil and water wells, expanded the existing injection production well spacing, changed the streamline and displacement direction, in order to achieved the purpose of expanding the swept volume of water drive and enhancing oil recovery. The results of numerical simulation show that: After fifteen years of production, the recovery rate of asynchronous injection production is 28.63%, which is 3.21%, 0.82%, 0.21% higher than that of depletion production, continuous water injection and conventional periodic water injection respectively. The field test shows that the pressure disturbance caused by the asynchronous unstable injection production adjustment is beneficial to the injection water entering the reservoir with poor physical properties, meanwhile, it can also improving the injection water utilization rate, expanding the swept volume, and alleviating the injection water breakthrough along the high permeability layer effectively, individual wells in the test area reduced water cut up to 22%, it is of great significance for promotion.

K carbonate reservoir in Middle East is a low permeability reservoir with thief layer. It is developed by waterflooding with a horizontal row well pattern. However, due to the influence of the thief layer, the water breakthrough fast, and the water cut rises to more than 40

X Oilfield is located in Persian Gulf Basin, a stable continental shelf region in the northern margin of Arabian Plate. It is an important oil-producing area in the middle part of Mesopotamia Basin. K formation is the major oil-bearing carbonate reservoir in Cretaceous Period. A method has been established to identify the fractured reservoir zone based on static and dynamic data analysis, which determine the reservoir types and fracture distribution in K formation. This research indicates that: 1. The production zones comprise two types of vertical fractures: large-scale fractures and small-scale micro fractures. The large-scale fractures are mainly developed along the faulted zone while the small-scale micro-fractures extend to the whole formation. Therefore, the main reservoir type in K formation is fracture-porosity reservoir which micro fracture is connected by the matrix pore. 2. The vertical small-scale micro fractures control the water flow direction and the development of water flow channel in the process of water injection. The fracture-porosity reservoir type determines the characteristics of oil producer that produce oil without water in a short period and water content with rapid increasing. However, the water rising rate decline year by year. The annual average water cut rate maintain at 2% when the water cut reach to 60%–70%. 3. K formation will preserve in the middle and high-water production stage for a long time. Thus, the key process to stabilize the oil recovery is to supply the formation energy through water injection.

High permeability layer and micro-fracture are important factors affecting water injection development in carbonate reservoirs. It is an important basis for recognizing and evaluating this kind of reservoir, improving its utilization degree and ensuring its development effect to clarify the characteristics of water drive flow in this kind of reservoir. Steady high permeability zones are developed laterally in K reservoir of a Middle East oilfield, and micro-fractures are developed in reservoirs with high structural position. Stereo injection-production pattern of horizontal wells with bottom injection and top production is adopted [1]. In recent years, some key problems have emerged in the process of oilfield development, such as rapid increase of water cut and low recovery. Based on the four flow channels of pore, micro-fracture, high permeability and pore, high permeability layer and micro-fracture in this paper. The law of water cut rising in production wells is summarized. To establish the model of oil saturation and resistivity by using wells. Comparative Analysis of Logging Curve Characteristics, the driving mode of injection water is established and the distribution characteristics of remaining oil are summarized. In conclusion, the flooding regime is summarized as follows: the fractures constitute vertical flow highways for the injected water, and the high permeability layer constitutes the horizontal flow highway. Providing guidance for development and evaluation of similar reservoirs.