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Collaborating Authors
Tight gas
The characteristics of the tight gas reservoir with strong heterogeneity and its 3D recovery technology in Yanโan gas field, China
Wang, Xiangzeng (Shaanxi Yanchang Petroleum (Group) Co. Ltd.) | Du, Yonghui (Shaanxi Yanchang Petroleum (Group) Co. Ltd.) | Zhang, Lei (Shaanxi Yanchang Petroleum (Group) Co. Ltd.) | Qiao, Xiangyang (Shaanxi Yanchang Petroleum (Group) Co. Ltd.) | Liang, Quansheng (Shaanxi Yanchang Petroleum (Group) Co. Ltd.) | Sun, Ping (Shaanxi Yanchang Petroleum (Group) Co. Ltd.)
Abstract The Yanโan gas field is located in the southeastern part of the Ordos Basin of China. After years of research, we have clarified the characteristics of the upper Paleozoic tight sandstone reservoirs: four main sets of intervals, including the Carboniferous Benxi Formation, the Shan second and Shan first members of the Permian Shanxi Formation, and the He eighth member of the Permian Lower Shihezi Formation, are multilayer complex superposed tight sandstone reservoirs that developed under the control of multiple differential sedimentary systems. Compared with the northern gas field, the upper Paleozoic reservoir is characterized by the small-scale effective sand body and poor physical property in the Yanโan gas field; the heterogeneity of the upper Paleozoic tight reservoir varies greatly: the heterogeneity of the He eighth and the Shan first members was increasing from the north to the south of the research area, owing to the intersection of the north and south provenance. The Shan second member indicates an obviously opposite trend: the heterogeneity of the Benxi Formation weakened from the center to both sides; the Yanโan gas field developed four main superposed composite sand bodies types, including the vertical superposed, lateral migration, cut superposed, and isolated types. Due to the existence of the interlayers rich in mudstone and soft debris near the architectural boundary, the reservoir sand body has strong structural heterogeneity under the interaction of differential diagenesis and densification. Aiming at the strong heterogeneity and multilayer complex superposition characteristics of the Yanโan gas field, we have made clear the constraints and matching relationships between control factors and well-pattern elements on the basis of deep analysis. We have formed the hybrid well pattern for 3D recovery technology that unlocked multilayer complex superposed tight sandstone gas reservoirs with strong heterogeneity in the southeastern portion of the Ordos Basin.
- Asia > China > Shaanxi Province (0.70)
- Asia > China > Shanxi Province (0.47)
- Asia > China > Gansu Province (0.47)
- Asia > China > Inner Mongolia (0.46)
- Asia > China > Shanxi > Ordos Basin (0.99)
- Asia > China > Shaanxi > Ordos Basin (0.99)
- Asia > China > Inner Mongolia > Ordos Basin > Wushenqi Field (0.99)
- (31 more...)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Tight gas (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Geologic modeling (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Exploration, development, structural geology (1.00)
A Novel Approach to Estimate Reserve and Forecast Production for Unconventional Gas Reservoirs by Developing New Reserve Correlation and Decline Model
Khalil, Hazem Mohamed (South Valley Egyptian Petroleum Holding Company) | Abdel Fattah, Khaled Ahmed (Faculty of Engineering, Cairo University) | Abdel Aziz, Abdel Aziz Mohamed (Faculty of Engineering, Cairo University) | Dahab, Abdel Sattar Abdel Hamid (Faculty of Engineering, Cairo University)
Abstract With the continuous increase in the worldwide demand for natural gas due to continuous natural decline of the conventional gas reservoirs, petroleum companies are turning their attention to unconventional gas resources. Reserve estimation in unconventional reservoirs is the most important during the development of unconventional reservoirs because the reserve affects project economics. The estimation of reserves in unconventional reservoirs is challenging due to the long production period required to estimate reserve accurately. The main goal of this work is the development of a new Decline Curve Analysis (DCA) models and a new Estimated Ultimate Reserve (EUR) correlation to forecast production data in unconventional gas reservoirs early and accurately. Recent decline curve analysis methods suffer from the limitation in use as they need a long production period to give accurate results and their calculations don't depend on the data of a reservoir's properties, the well and completion parameters, which are different from one reservoir to another. Several simulation models that model production from Multi Fracture Horizontal Wells (MFHW) are used to generate data representing different unconventional gas reservoirs. This data is used to study the effect of the reservoir and hydraulic fracture properties on the performance of unconventional gas reservoirs, then the most important parameters are used to build the EUR correlation and new decline models. The traditional decline models do not take into consideration the reservoir and completion parameters and need a long production period to achieve a good forecast. The new decline models were developed to eliminate these limitations through developing new decline models that include reservoir parameters such as reservoir permeability and initial reservoir pressure. The novel EUR correlation is different from other published studies in that, the focus was not on the estimating EUR using well production data, but the focus was on estimation of EUR using reservoir and completion properties. Using this newly developed correlation, reservoir engineers can estimate the reserve before drilling using well design, completion, and reservoir parameters. The newly developed DCA and EUR correlation has been tested and verified using different numerical simulations and field data. For this validation cases, the production data is used to compare the new approach and the other widely used decline models, which indicate the accuracy of this new approach. The advantages of these new developed DCA models are good accuracy compared to other DCA models because the new developed models depend on reservoir properties and this accuracy is achieved using short production history. This advantage helps better economic evaluation and well optimization of these unconventional resources as one of the important applications of these new approaches.EUR correlation is one of the first correlations developed for UGR and will help engineers for better economic evaluation and well optimization of these unconventional resources.
- Geology > Petroleum Play Type > Unconventional Play > Shale Play (0.46)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock (0.33)
Stephen Holditch, Professor Emeritus of Petroleum Engineering at Texas A&M University, held the Directorship of the Texas A&M Energy Institute, and was Head of the Harold Vance Department of Petroleum Engineering, where he supervised research in the areas of unconventional gas reservoirs, well completions, well logging and well stimulation, and hydraulic fracturing.
This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 205586, โRemote-Controlled Automated Foam Injection: A Digital Solution to Liquid Loading in a China Unconventional Gas Development,โ by Jiang Wei Bo, Beryl Audrey, SPE, and Uzezi Orivri, Schlumberger, et al. The paper has not been peer reviewed. Gas field C is an unconventional tight gas reservoir in central China. Horizontal-well multistage hydraulic fracturing has proved effective in this field. However, with continuous production over time, reservoir pressure declines, which results in a decrease in gas production rate below the critical gas velocity, leading to accumulation of liquid in the wellbore (liquid loading), which in turn results in backpressure and formation damage. To mitigate these challenges, a versatile intelligent dosing technology has been piloted to reduce liquid loading. Field Issues The field produces from four main reservoirs: Benxi, S2, S1, and H8, as shown from bottom to top in Fig. 1, at depths of between 7,850 and 10,816 ft, with an average thickness of 7.5 m. The porosity of S1 is between 2โ6% and permeability is less than 0.03 md, similar to that of H8. S2 (a subreservoir) features similar porosity as S1, but a higher permeability of approximately 0.3 md. Horizontal wells with multistage fracturing completions are used to develop the main reservoir, S2, whereas slanted wells are used to develop the other reservoirs in a commingled manner. This fieldโs first gas production was in July 2018. The current average daily gas production at the time of writing is approximately 132 MMscf/D. By the middle of 2021, the total number of gas production wells had reached 211, with approximately 10% of the wells shut in and waiting on well interventions. Two well completion types are used in the field, deviated and horizontal. The deviated wells are completed with 5ยฝ-in. casing and 2โ -in. tubing, or 3ยฝ-in. TAP lite and fractured. The horizontal wells feature an openhole completion with 3ยฝ-in. upper casing and 4ยฝ-in. down casing with fracturing. According to a recent analysis, 43% of production wells in the field experience liquid loading. Some are either shut in because of lack of gas production, while others produce intermittently because of depleted reservoir pressure. Wellhead-gas-sample analysis indicates that most of the produced gas is dry gas (i.e., no condensate liquid production). However, average field-flowback percentage after fracturing operations is only 40%, which means that 60% of the fracturing fluid is still in the formation when the well is brought online. Production-liquid-sample analysis suggests that the cause of liquid loading is low post-fracturing flowback ratio. Several deliquefication methods have been applied, such as velocity-string installation that reduces the critical unloading gas flow rate, soap or foam lift (either solid soap stick or liquid soap injection) that reduces the liquid density, and multirate well-testing equipment that increases the gas flow rate above the critical unloading gas rate. At the initial implementation of soap sticks, it was observed that incremental gas production was below expectations. This poor response was judged to be the result of the dosing quantity, and frequency trial-and-error judgments of the operators.
Gas field C is an unconventional tight gas reservoir in central China. Horizontal-well multistage hydraulic fracturing has proved effective in this field. However, with continuous production over time, reservoir pressure declines, which results in a decrease in gas production rate below the critical gas velocity, leading to accumulation of liquid in the wellbore (liquid loading), which in turn results in backpressure and formation damage. To mitigate these challenges, a versatile intelligent dosing technology has been piloted to reduce liquid loading. The field produces from four main reservoirs: Benxi, S2, S1, and H8, as shown from bottom to top in Fig.
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Tight gas (1.00)
- Production and Well Operations (1.00)
A Quantitatively Determining Gas Saturation Method Using Pulsed-Neutron Element Logging in Tight Gas Reservoirs
Zhang, Feng (School of Geosciences, China University of Petroleum) | Zhang, Hui (School of Geosciences, China University of Petroleum) | Qiu, Fei (School of Geosciences, China University of Petroleum) | Chen, Qian (School of Geosciences, China University of Petroleum)
Abstract Tight sandstone and carbonate gas reservoirs are important types of unconventional oil and gas, and their exploration and development are of great significance to increase production and economic development. It is difficult to accurately determine gas saturation for tight gas reservoirs due to their low porosity and permeability, which differs from conventional reservoirs. In the past few decades, pulsed neutron logging technology is one of the most important means to evaluate gas saturation, especially the ratio of gamma-ray counts from pulsed neutron logging tool with long spacing detector was generally used to improve detection sensitivity for quantitatively evaluating gas saturation. However, there are complex formation minerals and pore fluid composition in tight sandstone and carbonate reservoirs, and then it will obviously affect gas saturation evaluation. In the previous study, we introduced a three-detector pulsed neutron consisting of a DT pulsed neutron generator, two He-3 thermal neutron detectors, and a LaBr3 detector located between the two thermal neutron detectors. The logging tool performs elemental measurement. In addition, the formation porosity was calculated according to the information of gamma ray and thermal neutron detected by the three detectors in previous research. In this paper, the thermal-neutron ratio of near to extra-far detector and the lithology factors from elemental yields based on the measuring information from three detector are also used to determine gas saturation and eliminate the influence of lithology. The SuperMC software is employed to build three-dimension model with the pulsed neutron tool and formation which contains different minerals, gas saturation and salinity to obtain the responses of thermal neutron and gamma-ray under complex formation conditions. In addition, the spectrum of the inelastic gamma and capture gamma are used to acquire the yields of elements, such as iron, silicon, potassium, aluminum, magnesium, calcium and carbon. The regression coefficients of different elements are obtained from the relationship between the ratio of thermal neutron count ratio and the ratio of elemental yield of the formation, which is combined with the information of thermal neutron count ratio and elemental yield to build a new interpretation model for gas saturation. The new model eliminates the influence of lithology and improves the accuracy of gas saturation determination. A complex formation containing quartz, calcite, plagioclase, chlorite and pyrite with 12% porosity and 50% gas saturation is evaluated by the conventional interpretation model with 0% gas saturation, while the interpretation model proposed in this paper evaluates 48% gas saturation, and the relative error is reduced from 100% to 4%. Finally, a field example of a tight gas reservoir from Shanxi verifies the accuracy of the new model of gas saturation.
- Geology > Mineral > Silicate (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Sandstone (0.93)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Tight gas (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Exploration, development, structural geology (1.00)
- Reservoir Description and Dynamics > Formation Evaluation & Management > Open hole/cased hole log analysis (1.00)
Case Study: Analysis of Refracturing Crack Orientation-Angle and Extension-Length in Tight Gas Reservoir, Sulige Gasfield of China
Wang, Yang (State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum Beijing, China) | Yao, Yuedong (State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum Beijing, China) | Wang, Lian (State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum Beijing, China) | Hu, Yongquan (Southwest Petroleum University, Chengdu, China) | Wu, Hao (CNOOC Research Institute Co., Ltd., Beijing, China) | Wang, Hao (1st Gas Production Plant of Changqing Oilfield Co., Ltd., Xi'an, China)
Abstract Attribute to the hydraulic fracturing technology, China has carried out commercial development of the low permeability and tight gas reservoirs in Sulige Gasfield, Ordos Basin. However, the practice indicates that the gas well with hydraulic fracturing performs rapid decline rate, which generally repeated fracturing technology is often adopted to enhance the economic benefits of gas field development. Therefore, the reservoir physical properties, pressure system, fluid properties, and formation parameters of fracturing engineering, such as rock characteristic parameters and original in-situ stress, are respectively summarized. Furthermore, compared with traditional hydraulic fracturing, the theory of refracturing and the simulation of crack extension are studied. This study starts from the geological characteristics, gas reservoir properties and rock physical properties of the main layer. Firstly, based on the theory of rock elasticity, the problem of crack induced stress field is analyzed. Then, combined with the rock media and mechanical environment around the initial artificial crack, the mathematical model of the induced stress field of the initial artificial crack is established. Meanwhile, the semi-inverse solution is applied to solve the mathematical model. Finally, the analytical formula of crack induced stress is obtained, by introducing Fourier transform, complex variable and Bessel function integral formula. Taking a fractured gas well in Sulige Gasfield as an example, only single-phase gas flowing is considered and depletion constant pressure production is adopted. The results show that: (a) The induced stress is mainly related to the net pressure on the crack wall, in which the induced stress in the direction of the original horizontal principal stress increases with the net pressure. (b) Through the simulation of tight gas reservoir performance, we found that the change of production induced stress is great with the longer production time, the lower bottom-hole flowing pressure and the more variable anisotropy of reservoir permeability. (c) The area of in-situ stress reorientation is also greater, and the new crack gets easy to change direction. (d) This simulation can help engineers realize that the initial artificial crack induced stress and gas well production induced stress all change the initial in-situ stress, thence, the new crack of refracturing will not fracture along the direction of the old crack. In this case, the Orientation-Angle and Extension-Length are recalculated, after calculating the current stress state in the direction of the original principal stress, and production time, bottom hole production pressure and others that affect the new crack are analyzed. More importantly, this research could be applied for other similar refracturing wells with vertical cracks in tight gas reservoirs worldwide and provides a research basis for the afterward study of the description of volumetric crack.
- North America > United States > Texas (1.00)
- Asia > China > Inner Mongolia (0.92)
- North America > United States > Texas > Permian Basin > Yeso Formation (0.99)
- North America > United States > Texas > Permian Basin > Yates Formation (0.99)
- North America > United States > Texas > Permian Basin > Wolfcamp Formation (0.99)
- (37 more...)
- Well Completion > Hydraulic Fracturing > Re-fracturing (1.00)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Tight gas (1.00)
Data science continues to provide solutions for unconventional-well challenges. But innovative combinations of proven technologies also are delivering improved success in artificial lift wells. The articles I have selected for this feature provide details on these achievements. But can the learnings from one type of completion improve success in other types of completions? The shale gas revolution is over 20 years old. The pace of innovation has been rapid, and many technologies and methods have been developed that reduce completion time and maximize access to the reservoir with one well. Unconventional-well innovation, therefore, has led to constant improvements in efficiency and reliability. There is no doubt this will continue, but can unconventional learnings be applied in conventional completions? Electrical submersible pumps (ESPs) and intelligent-completion technologies are complementary, but each have very different service lives. For example, intelligent-completion hardware may have a 20-year service life, while ESPs may have a 2-year service life. So how can they be integrated in a way that ensures long-term reliability in the intelligent completion while accommodating periodic ESP workovers? Reimagining completion architecture is one way that a Middle East operator has achieved this goal. Can large logging-while-drilling and measuring-while-drilling data sets be used to optimize completion of the well? One paper explains how perforation cluster design in Marcellus wells can be optimized by analyzing these data sets using a convolutional neural network model. The key to optimization involves mechanical specific energy. Is the lesson here to drill with the completion in mind or to complete with drilling in mind? Will drilling engineers and completion engineers answer the last question differently, or will they agree on a different paradigm for the next well or project? It has been said that you will get the same result by repeating what you have done. But if you want to have a better result, you must change what you are doing. Is it time for a paradigm shift? Recommended additional reading at OnePetro: www.onepetro.org. SPE 199712 - Evaluating Limited-Entry Perforating and Diverter-Completion Techniques With Ultrasonic Perforation Imaging and Fiber Optic DTS Warmbacks by Chase Murphree, SM Energy, et al. SPE 207862 - Modeling a Novel Approach To Delay the Water Breakthrough in Gas Cap Wells Using Smart Completions: Case Study Onshore Abu Dhabi Field by Aditya Ojha, ADNOC, et al. SPE 201268 - DTS Flow Profiling for a Horizontal Multistage Fractured Well in Tight Gas Reservoirs by Improved Model Considering an Openhole Packer Completion Scenario by Weibo Sui, China University of Petroleum, et al.
- Asia > Middle East > UAE > Abu Dhabi Emirate > Abu Dhabi (0.26)
- Asia > Middle East > Kuwait > Jahra Governorate (0.26)
Addressing the Challenges of Hydraulic Fracturing Vertical Wells in Differential Depleted Tight Gas Accumulations in Oman
Al Bahri, Khalfan (Petroleum Development Oman) | Chaves, Juan (Petroleum Development Oman) | Al Hinai, Adnan Saif (Petroleum Development Oman) | Al Sulaimani, Ahmed Abdullah (Petroleum Development Oman) | Nunez, Alvaro Javier (Petroleum Development Oman)
Abstract Hydraulic fracturing has been a key technology enabler for the development of tight gas formations in Oman. This tight gas accumulation has been developed with the supported of vertical wells, fractured at different depth covering up to 10 different hydrocarbons units. The intrinsic geomechanical, petrophysical and lithological heterogeneities of this tight units impact not only the fracture conductivity distribution but the drainage efficiency of the fractured zones, this is observed as mobility variations across this unit impact their contributions once all become commingle, with the areas of higher mobility dominating the total gas well production. It was anticipated that depletion of the higher mobility units will impact and change the contribution dynamics of the commingle production. However, this is only one dimension of the challenges to be considered as part of the hydraulic fracture strategy during the field development. This paper will be focus key operational challenges and the fundamental formation characterization requirements to assess in-situ stress dynamic variations during the life of the field; incorporating formation pressure points as integral part of the drilling program and in-situ stress measurements supported by wellbore stability evaluation and mini-fracture operations. It will be presented how variations on pressure and stress profiles, as the field developed, will impact the perforation and fracture strategies as well as pressure operating envelop to assure well integrity. It will be described the logging requirements as well as the lab characterization needed to determine key elastic properties to assess the hydraulic requirements for fracturing individual units or combination of them. It will be discussed how increase of pressure confinement potentially affects the in-situ elastic properties as depletion is experienced on specific gas units, inducing alterations on stress profiles that impact fracture propagation and final conductivity distribution. The use of radioactive tracers in combination with production logging were implemented to assess containment and fracture prediction, providing this an essential tool to determine fracture propagation behavior, deployment strategy and final conductivity distribution. Key operations covering plug milling, post fracture clean out and well lifting will be also discussed. Finally, it will presented key observation that can be implemented as part of methodologies used for fracture deployment on differential depletion formation, this leading to optimum field development while maximize investment.
- North America > United States (1.00)
- Asia > Middle East > Oman (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (0.49)
- Asia > Middle East > Oman > Ghaba Salt Basin (0.99)
- Asia > Middle East > Oman > Central Oman > Barik Formation (0.99)
- Asia > Middle East > Oman > Miqrat Formation (0.97)
- (2 more...)
Petro-Phyiscal Evaluation Methods of Complex Clastic Deep Tight Gas Reservoirs to Improve Hydraulic Stimulation Efficiency
Al Hinai, Adnan Saif (Petroleum Development Oman) | Abdelazim, Mohamed Fathy (Petroleum Development Oman) | Al Aamri, Mohammed H. (Petroleum Development Oman) | Al Wahaibi, Ahmed Mahfoudh (Petroleum Development Oman)
Abstract In most cases calstic deep tight gas reservoirs contain considerable hydrocarbon reserves but the ultra-low permeability and the poor inter-connection between the pores may dramatically reduce the recovery for economical gas production. In such cases, hydraulic stimulation techniques can be beneficial to improve the connectivity between the pore spaces and provide a larger conductive channel to allow communication between the reservoir and the well bore. Prior to the fracturing design it is imperative to understand the borehole and the reservoir environment. Hence, the application of petro-physical evaluation. The main objectives of this paper is to discuss the petro-physical evaluation; conventional and advanced methods to understand fracture initiation and propagation behaviors that are essential to plan, design and execute an effective hydraulic fracture treatment program. A large range of wireline logging tools are available today, and several provide sophisticated interpretations of the formation; including details of formation lithology, fluid type, porosity, fluid content and stress regime, etc. In this paper, integrated interpretation has been conducted from both open and cased hole wireline logging. With the aim of assessing the rock mechanics, formation pressures, cement bond, well bore integrity and other reservoir properties to establish a prominent fracturing zone in Barik and Miqrat tight gas reservoirs. Post fracture analysis such as radioactive tracers has been demonstrated, production logging and noise log are studied and linked with the amount of proppant placed in the selected fracturing intervals to assess the stimulation efficiency. Cement bond log evaluations showed good zonal isolation across the 4.5" tubing in the studied wells, notably in Barik and Miqrat reservoirs. However, poor to intermediate cement was observed across the overlap section between 9 5/8" and 4.5". In which was not a stimulation obstacle. Saturation and electrical parameters were derived from Archie's equation and Special Core Analysis (SCAL), respectively. The interpretation revealed that Barik and Middle Miqrat formations are relatively conclusive in some fields and not in others. Mainly due to the high saturation of the trapped gas due to the tightness of the reservoir. Moreover, based on the saturation log analysis, porosity controlled hydrocarbon saturation profile and created a challenge in determining the top of water bearing interval. Non-resistivity based saturation estimates, such as pulsed neutron and dielectric logs did not offer benefit in fluid typing. Well test showed different results as compared with the anticipated water and gas rates. Gas inflow was observed in all tested wells. In addition, some wells not-necessarily located in the extreme flanks of the field, showed high water influx. Irreducible water saturation derived from NMR and/or capillary pressure data helped to identify moveable water in Barik but not in Lower Miqrat formation due to presences of bitumen and vugs. Selective completion strategy for hydraulic stimulation proved to be successful by screening the reservoir intervals thru the use of a combination of petrophysical and cased hole production analysis. Allowing hydraulic fracturing execution to achieve up 90% of the desired proppant placement. Knowledge of in-situ stresses (magnitudes & directions) is critical to understand hydraulic fracture initiation & propagation behaviors. The initiation and propagation behaviors are essential to plan, design and execute an effective hydraulic fracture treatment program. Open hole and cased hole logging are key practices for evaluating fracture behavior. It provides the grounds to optimize for future wells for stimulation.
- Geology > Rock Type > Sedimentary Rock > Clastic Rock (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Asia > Middle East > Oman > Al Wusta Governorate > Hazar Field (0.99)
- Asia > Middle East > Oman > Miqrat Formation (0.96)
- Asia > Middle East > Oman > Al Wusta Governorate > Arabian Basin > Rub' al-Khali Basin > Barik Field > Barik Formation (0.94)