Wei, Chenji (Research Institute of Petroleum Exploration and Development, CNPC) | Zheng, Jie (Research Institute of Petroleum Exploration and Development, CNPC) | Ouyang, Xiaohu (China Petroleum Pipeline Engineering Co., Ltd, CNPC) | Ding, Yutao (China National Oil and Gas Exploration and Development Company Ltd. CNPC) | Ding, Mingming (China National Oil and Gas Exploration and Development Company Ltd. CNPC) | Lin, Shiyao (China National Oil and Gas Exploration and Development Company Ltd. CNPC) | Song, Hongqing (University of Science and Technology Beijing)
Understanding the heterogeneity is critical for a successful water injection in a carbonate reservoir. Thief zone is one of the most obvious forms of heterogeneity, which indicates the thin layer with higher permeability compared to the average reservoir permeability. The existence of thief zone results in earlier water breakthrough and faster water cut increase, which then lead to lower sweep efficiency and smaller recovery factor. Therefore, determining the distribution of thief zone and its impact towards production, and proposing a corresponding development plan are very important.
In this paper, a novel method is established to determine the thief zone distribution based on dynamic surveillance data. A new index is proposed as the relative contribution index to characterize the relative contribution of a certain layer, which is fundamental for thief zone determination. In addition, effect on water flooding development of thief zone's location is studied by experimental and theoretical analysis. The changes of water cut and production rate are analyzed under different conditions such as location of the thief zone, injection rate, and variogram. Finally, optimized development strategy is proposed to deal with the existence of thief zone.
Distribution of thief zone is characterized based on the proposed method, which indicates that thief zone development has intimate relationship with depositional facies and diagenesis. Experimental and theoretical analysis results show that the present model considering stratified water-flood is consistent with the experimental results. The water displacement effect is the best when the thief zone is located in the upper reservoir. This paper also points out the optimal adjustment period for water shutoff and profile control of the reservoir with thief zones. In addition, the greater the injection rate, the faster the water cut increase. Furthermore, the smaller the variogram, the slower the water cut increase, and the later the water breakthrough time.
This study provides a method to characterize thief zone, which can be used as a reference for similar oilfield development. In addition, it provides a quick and reasonable guide in the later adjustment of water flooding development of carbonate reservoirs with thief zones.
Identification of tidal channels fairways is key for predicting behavior of areas at higher risk to water breakthrough or otherwise have a significant impact on the development and monitoring of reservoir performance. However, tidal channels in carbonates are not often easily characterized using conventional seismic attributes. It is important to decipher the complexity of the carbonate tidal channel architecture with integrated multisource data and a variety of approaches.
In this paper, petrological characteristics and petrographic analysis is conducted on well logs and validated carefully using core data. Then, the second step is to compare the carbonate channel systems with modern analogue in Bahama tidal flat and outcrop scales in Wadi Mi'Aidin (Northern Oman). Thereafter, the supervised probabilistic neural network (PNN) and linear regression method were undertaken to detect an additional channel distribution.
The relationship of high porosity with low acoustic impedance appeared mostly in the channel facies which reflects good reservoir quality grainstone channels. Outside these channels, the rock is heavily mud filled by peritidal carbonates and characterized by a high acoustic impedance anomaly with low quality of porosity distribution. The new observation of PNN porosity volume revealed a lateral distribution of the Mishrif carbonate tidal channels in terms of paleocurrent direction and the connectivity. Additionally, the prior information from core data and the geological knowledge indicate a good consistency with classified lithology. These observations implied that Mishrif channels consist of a wide range of lithology and porotype fluctuations due to the impact of depositional environment.
The work enables us to provide a new insight into the distribution of channel bodies, and petrophysical properties with quantification of their influence on dynamic reservoir behavior of the main producing reservoir. This work will not only provide an important guidance to the development and production of this case study, however also deliver an integrated work path for the similar geological and sedimentary environment in the nearby oil fields of Southern Iraq.
This seminar will teach participants how to identify, evaluate, and quantify risk and uncertainty in everyday oil and gas economic situations. It reviews the development of pragmatic tools, methods, and understandings for professionals that are applicable to companies of all sizes. The seminar also briefly reviews statistics, the relationship between risk and return, and hedging and future markets. Strategic thinking and planning are key elements in an organisation’s journey to maximise value to shareholders, customers, and employees. Through this workshop, attendees will go through the different processes involved in strategic planning including the elements of organisational SWOT, business scenario and options development, elaboration of strategic options and communication to stakeholders.
Decisions in E&P ventures are affected by Bias, Blindness, and Illusions (BBI) which permeate our analyses, interpretations and decisions. This one-day course examines the influence of these cognitive pitfalls and presents techniques that can be used to mitigate their impact. Bias refers to errors in thinking whereby interpretations and judgments are drawn in an illogical fashion. Blindness is the condition where we fail to see an unexpected event in plain sight. Illusions refer to misleading beliefs based on a false impression of reality.
The objective of this work is to characterize the porosity distribution and the types of carbonate facies in the Mishrif Formation in the West Qurna/1 Oil Field using seismic inversion results, well log data and rock physics modeling. Identification of the pore system and the spatial distribution of lithofacies are keys for constructing Mishrif reservoir model, which have a great impact on the development of the most prolific reservoir in the field (Mishrif zone).
Seismic inversion involves the interpretation of elastic properties for facies based on the seismic response. It enables the modelling of lithology and porosity distribution in 3D space away from well control. In order to achieve the aim of the work, a step wise approach will be taken. First of all, deterministic seismic inversion was applied across the high resolution of 3D-seismic survey data over the West Qurna/1 Field. Then, the vertical distribution of porosity and facies recognition based on well log data and its relationship with elastic properties, integrated with seismic inversion results for validating at Mishrif intervals.
Deterministic seismic inversion was undertaken on the post-stack seismic dataset. The interpretation of seismically derived characterization in Mishrif reservoir indicated a different lateral distribution of acoustic impedance and three regions of channel (north, southwest and east). It can be seen a high acoustic impedance anomaly outside the channel in the western field sector which is heavily mud supported by peritidal carbonates (low quality facies of the reservoir). Whereas, carbonate tidal channel displayed a low acoustic impedance which reflect high porosity and good reservoir quality (grainstone channel or sholas). Furthermore, the interpretation of the well log and rock physic model was correlated with seismic inversion volume in terms of the lithology and porosity. Consequently, some zones which included carbonate tidal channel, displays a wide range of porosity and lithology fluctuations due to the impact of depositional environment (subaerial exposure).
The workflow provided insight into the distribution of petro-physical properties and quantification of their influence on dynamic reservoir behavior. The results also indicated the areas of high permeability and its component that may include fractures or connected vug systems. Water flood design and completion strategies (well trajectories) will be developed and succeeded according to the heterogeneous geological regions. Overall, this will ultimately lead to improve the development plan of wells in terms of production performance, recoverable reserves and economic value.
Just a week before the World Petroleum Congress in Istanbul, Volvo announced that it will phase out its production of petrol and diesel cars from 2019. Several weeks before that, a famous energy futurist from Stanford University, Tony Seba, predicted the end of the oil industry by 2030. Working in an oil and gas company in 2017 and frequently hearing such news stories can certainly seem to be a cause for great concern. Thankfully, the ability to adapt is one of the oil and gas industry's greatest strengths. Despite this, however, the oil field resiliently dominates commodity markets.
This article exclusively relies on data from published literature.
The development of a foreland basin in the Mesopotamian Basin of South Iraq during the deposition of the Mishrif resulted in facies stacking patterns reflecting the development of a flexural bulge.
Paleogeographic reconstructions rely on carbonate facies as depth indicators, whereby rudist biostromes and coarser bioclastic debris define Shoal Complexes that separate restricted lagoonal deposits from open marine sediments. Ahmadi-Rumaila-Lower Mishrif sediments deposited into a N-S trending basin also showing evidence of precursory foreland basin tectonics: the increasing thickness of Lower Sequence deposits to E and NE reflects an increase of accommodation space in these areas. A disconformity separates the lower and upper Mishrif sequences, and represents the initiation of the flexural forebulge. The lower sequence (Mishrif mC, mB2) is characterised by a N-S oriented platform margin Shoal Complex, while during the upper sequence (Mishrif mB1, mA), a NW-SE orientation prevailed. The origin of the regionally deeper facies at the start of the Upper sequence reflects eustatic sea level rise, after which foreland basin tectonics significantly changed the paleogeography of the basin and enabled the rudist Shoal Complex to spread over a wider area. The Mishrif caprock at the top of the Upper Sequence represents a major regional exposure.
Alpine 1 tectonic activity, previously associated with the Khasib, Tanuma, Sadi and Hartha Formations in the region, actually initiated earlier, impacting the upper and to a lesser extent lower Mishrif sequences. The activity is interpreted in a foreland basin setting, with structural styles similar to but smaller scale than that seen later in the Alpine 2 Zagros emplacement.
Local structuration effects along pre-existing lineaments likely reactivated in different orientations due to the rotating stress fields. NW - directed push leading into Alpine 1 on N-S oriented structures may have resulted in transpressional strike slip related uplift. Such local uplift cannot however explain the observed facies stacking patterns, particularly in the Upper Mishrif.
Yaping, Lin (Research institute of petroleum exploration & development, CNPC) | Liangdong, Zhao (Research institute of petroleum exploration & development, CNPC) | Liyong, Tan (CNPC Greatwall drilling company) | Jiangyuan, Yao (Research institute of petroleum exploration & development, CNPC) | Man, Luo (Research institute of petroleum exploration & development, CNPC) | Jiping, Wang (Changqing Oilfield Company, PetroChina)
Based on cores lab data observation, depositional facies analysis, lithotypes analysis and well logging data, the characteristics of lithotypes and lithofacies of carbonate reservoirs Carboniferous Unit B formation of K oil field in the southern margin of Kazakhstan Caspian basin are described and summarized, the identification standards of lithotypes and lithofacies by using well logging are established. The main lithofacies in Unit B formation carbonate reservoir were classified into 6 types: compacted limestone, grainstone, reef limestone, wackestone/packstone, marlstone and mudstone. The lithotypes and lithofacies in Unit B formation in K oil field were analyzed both qualitatively and quantitatively by conventional logging and imaging logging and other methods. The discriminatory criteria of reservoir lithotypes and lithofacies were established by analyzing conventional logging and imaging logging data, summarizing the different facies lithology logging response characteristics, developing carbonate lithology structure index(CLSI) characterizing its quantitative characterization.
In this study, the depositional facies were analyzed: two main depositional environments developed in K field, which are platform and slope, and the dominant facies in this block can be divided into lagoon, tidal flat, intershoal depression, rim shoal, rim reef, the outer continental shelf and continental slope. The well log responses of each lithology and lithofacies were identified, the five different types were recognized by the above method. The identification and classification of lithotypes and lithofacies in both vertical and horizontal disturbition in UnitB formation were achieved by processing the logging data from each well in this block, the identification results of lithotypes and lithofacies were well matched the analysis of physical properties. This study is one of the important keys for the reserves calculation and the development plan, and also guides to evaluate the complex carbonate reservoir of K oil field.
The Rumaila field is located in South East Iraq and contains multiple reservoir intervals, including the Upper Cretaceous Mishrif carbonate. This reservoir has been on production for many years but still contains significant oil reserves. Reservoir pressure has dropped due to historical production and, therefore, large scale water injection is planned to support future production.
Full field models have been built in order to simulate the planned Mishrif water injection. These models were calibrated using available historical data, such as well production rates and conventional core plug permeability data. The first generation of models showed that the permeability measured with conventional core plugs could not always produce the historical production rates reported. This difference was interpreted as a dual permeability effect from vug networks, which is common in carbonate reservoirs but difficult to characterise by conventional core plugs. The pragmatic solution for the first generation of models was to apply crude permeability multipliers to selected reservoir layers that were suspected to have an enhanced permeability not represented by core. This enabled an acceptable match to historical production data but the distribution of these multipliers was non-unique. The distribution of these multipliers dominated water injection simulations but no historical water injection data was available to calibrate this affect. A more robust solution using an integrated approach was required to capture the heterogeneous permeability profile.