bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling Study of Wellbore Vortex Flow and Helical Angle Design of Downhole Vortex Tool
Authors: Zhou Chao , Zhang Tongyi , Wu Xiaodong , Zhao Fei , Xiong Xiaofei
Published: April 2019

Vortex drainage gas recovery is a new drainage gas recovery technology. However, its operating mechanism has not been figured out. Theoretical analysis of force condition of the liquid film in the wellbore vortex flow field is still lacking, and dynamic analysis method of the liquid film is not established. The objective of the proposed paper is to establish the liquid film dynamic analysis model and calculate the optimal helical angle of the vortex tool. Dynamic analysis of the liquid film in the wellbore vortex flow field is carried out on the basis of the flow pattern and force condition of the liquid film. Expression of each acting force is determined and the force equilibrium equation is obtained. Referring to the annular flow theory, friction coefficient and average thickness of the liquid film are calculated. Through derivation of the vertical resultant force equation of the liquid film, the optimal helical angle of the vortex tool is obtained. Then, vortex tools were designed and deployed in the wellbore of a gas well in field. Field study shows that the relative difference of the optimal helical angle obtained by liquid film dynamic analysis relative to that obtained by numerical simulation is less than 4%. The optimal helical angle calculated by the liquid film dynamic analysis model is reliable and provides guidance for the structure optimization of vortex tools. Optimal helical angle would increase with well depth decreases because of enhancement of fluid-carrying capability of the gas. The liquid film dynamic analysis model can reasonably explain the motion and force condition of the liquid phase in the wellbore vortex flow. Compared with the conventional annular flow field, vortex flow filed includes additional centrifugal force on the liquid film, which may benefit the upward motion of the liquid film. The liquid film dynamic analysis model in the wellbore vortex flow field and the formula for calculating the optimal helical angle of the vortex tool are established for the first time, whose results fill the gap in existing studies and have a guiding significance for optimization design and field application of vortex tools.
Risk Management in Deepwater Exploration Well: Reduced Depth Uncertainty Through Acquiring Seismic While Drilling
Authors: Purnomo Agung , Octaviani Tenny , Paterson Graeme , Pasaribu Ihsan Taufik , Mori Ryota , Ahmed Aqil , Akama Kenichi , Aini Muhamad Faizol Badrul
Published: April 2019

One of the key for successful drilling through carbonates build up structure is accurate time depth information to avoid kick-loss scenario during drilling if the carbonate is accidentally penetrated in the unexpected shallower hole size. Setting the casing point accurately to isolate the high overpressure regime on the overlying shale above the carbonate is required. During Kangean operation, Geostopping using Seismic While Drilling (SWD) technology was applied for setting the 9 5/8" casing before penetrating the Prupuh carbonate formation and updating the pore pressure model. This paper will demonstrate an application of SWD in Indonesia’s deepwater operation of predicting critical carbonate depth enabling well construction on time and on budget.

Acquisition of SWD was done during an acoustically ‘quiet’ period, during stand connections while pumps are off. Real-time waveforms are transmitted to surface through the mud telemetry system and sent to processing center via secure connection systematically after each seismic level acquired. Processing was done in real-time providing updated time-depth information, placing bit position on the seismic section in depth domain for refining depth prediction and ultimately Vertical Seismic Profile (VSP) corridor stack containing seismic reflectors along the wellbore and ahead of the bit for look-ahead information. The real-time updated interval velocity was used to update pore pressure model for monitoring the overpressured zone and to adjust mud weight accordingly while drilling to prevent a kick situation.

A total of 27 real-time SWD levels were acquired during drilling over interval ~1,800 ftMD. The data was found to be of a high quality that allowed for an accurate well tie of the Prupuh Carbonate top with a final depth prediction. Real time velocity showed that velocity of Cepu shale above the Prupuh carbonate was slower than pre-job velocity model, meaning that the Prupuh carbonate depth is shallower than initial prediction. Real time decision was made to set the casing before Prupuh Carbonate top. The actual Prupuh top was 23 ft deeper than the latest real time Prupuh prediction. This SWD technology allows us to reduce top carbonate uncertainty from +697 ft/-375 ft to become +/− 23 ft and ultimately saved the well from potential catastrophic event.

This study demonstrates that SWD technology give us confidence to manage risk in real-time.
Calibrated Natural State Model in Sorik Marapi Geothermal Field, Indonesia
Authors: Mulyani Sri , Sarmiento Zammy , Chandra Vicky , Hendry Ridha , Nasution Syukri , Hidayat Ryan , Jhonny Jhonny , Sari Pebrina , Juandi Dedi
Published: April 2019

Understanding the reservoir conditions through 3D subsurface modeling is the key to optimize the exploration stage in geothermal field. A calibrated reservoir model based on updated data can be very important for this process. The main challenge of reservoir characterization in a geothermal field is the lack of subsurface data, therefore surface data are useful for reservoir modeling. This study utilized Sorik Marapi geothermal field data as a reference for reservoir modeling. This field is one of the geothermal fields in Indonesia that has been recently drilled, with results indicating the existence of a high temperature-neutral acidity resource. Initial reservoir model has been built from the previous study to create conceptual 3D subsurface model which includes structural, lithology, resistivity, and temperature distribution from surface exploration data, including surface mapping, remote sensing image interpretation, the magnetotelluric method, and subsurface data from six wells data.

The objective of this paper is to calibrate the initial reservoir model with information from an additional ten new wells data to improve delineation for updated reservoir area in the field. Software that allowed multidisciplinary data integration from surface to subsurface information was used for the calibration of the initial 3D model. The workflow to calibrate the model started with data loading and quality control, preparing the old 3D model and comparing it to new well data, analyzing the comparison, and updating the 3D model. Finally, the new delineation of reservoir zone can be determined.

The result of this study is an updated 3D subsurface static model defining the vertical and lateral reservoir boundaries, as well as the prime resource areas, which would be the basis for designing future well targets, and parameters for a dynamic reservoir model. The same model can be expanded to construct the numerical model to match the natural state condition of the field and make forecasts of the future reservoir behavior at different operating conditions. The main properties of the updated 3D model are lithology and temperature, which are important in geothermal reservoir delineation.
Surge Peak Pressure Magnitude Impact due to Vapour Formation and Collapse: Simulation Study, Mitigation and Testing
Authors: Alwi Aqeela Hani , Philip Nicholas
Published: April 2019

A surge study was conducted for the addition of a new LNG storage tank in PETRONAS Malaysia LNG in Bintulu, Sarawak. With the new LNG storage tank being the largest, furthest, highest elevation and with the biggest LNG loading pump capacity, a thorough surge study is essential to ensure safe operations of the existing loading lines network.

During emergency situations, Emergency Shutdown (ESD) system may be activated where the ESD valves will be closed within 15 seconds to return the loading lines network into safe conditions. However, with the rapid closure of ESD valves, there is a sudden velocity change to the LNG liquid in the loading lines. This results in a vapour formation and collapse phenomenon which causes a surge pressure peak and resultant transient force onto the piping.

The surge study started with a simulation study, where it was found that the initial surge pressure may surpass the loading lines piping design pressure. Then, the simulation carries on evaluating the possible mitigation measures that could be applied to the loading lines network to reduce the surge pressure to safe operating limits below the piping design pressure. Once satisfied, an actual ESD test was conducted where the ESD situation is replicated and the actual surge pressure was recorded. This test serves to reaffirm the simulation study and possibly quantify the magnitude of surge pressure experienced in real ESD situations.

The mitigation measures of a 20 second pump delay timer and kick back valves to open during ESD activation was applied prior to the ESD test. During the test, the surge pressure peaks at approx. 20 barg, which was 4 times the normal loading pressure. This is as expected from the surge simulation considering mitigation measures are applied. If the mitigation measures were not applied, the surge pressure peak may go up to 10x the normal loading pressure, enormously exceeding the loading lines design pressure and may be catastrophic. Additional findings and discussion on the test results are presented in this manuscript.

In conclusion, the surge pressure magnitude experienced due to sudden velocity change may peak numerous times above the normal pressure even though only for a short time. This situation is applicable to LNG loading lines but is also possibly applicable to other liquid lines with sudden fluid velocity change within the piping. It is important to ensure that the necessary mitigation actions are taken prior to putting the lines into service.
Investigation of Multi-Scale Approach for Damage Control in Ultra-Deep Tight Sandstone Gas Reservoirs Based on the Multi-Scale Formation Damage Mechanisms
Authors: Zhang Dujie , Kang Yili , You Lijun , Li Xiangchen , Li Jiaxue , Chen Yashu
Published: April 2019

Cretaceous Bashijiqike ultra-deep tight sandstone, the main pay zone of Keshen gas field in Tarim Basin, has characteristics such as huge buried depth (6500 m ~ 8000 m), ultra-low matrix permeability and well-developed natural fractures. Due to lacking of a thorough research on the formation damage mechanism, there is no corresponding formation damage control method. And that's why this reservoir is suffering from severe formation damage. In this paper, the multi-scale characteristic of the reservoir space and seepage channel was described firstly. Then, a series of experiments were carried out to determine the multi-scale damage mechanisms, including the fluid sensitivity damage of matrix and fracture, the phase trapping damage of matrix and fracture, the loading capacity and the dynamic damage of fracture induced by drilling fluids. Then, the multi-scale formation damage mechanisms were summarized. Results showed the gas reservoir are characterized by typical multi-scale structures, i.e. micro-nano pore-throat and multiscale natural fractures. Severe salt sensitivity damage, alkali sensitivity damage and water phase trapping damage were the main damage mechanism of micro-nano pore-throat. For micro-fracture (aperture ≤ 100 μm), the dynamic damage degree induced by drilling fluids can reach up to 60.01 %. For Mesoscale fracture (aperture > 100 μm), lost circulation induced by inadequate loading capacity of drilling fluids was the main damage mechanism. Then, a complete multi-scale approach for damage control was proposed: ① Using oil-based drilling fluids to inhibit the fluids sensitivity damage and phase trapping damage of micro-nano pore-throat and natural microfracture; ②Optimizing the solid particle size distribution of drill-in fluid to reduce the dynamic damage degree of micro-fracture induced by drilling fluids; ③Adding acid soluble temporary plugging materials while drilling to prevent lost circulation. According to the proposed approach, the total production of the test well was 94 × 104 m3, which is much higher than that of non-test wells. This research provides a detailed case of forming the multi-scale approach for damage control based on the multi-scale formation damage mechanisms. This method is practical and useful, and it has important guiding significance to develop the ultra-deep fractured tight gas reservoirs efficiently.
Experimental Study of Sand Erosion in Multistage Electrical Submersible Pump ESP: Performance Degradation, Wear and Vibration
Authors: Zhu Haiwen , Zhu Jianjun , Zhou Zulin , Rutter Risa , Forsberg Michael , Gunter Shawn , Zhang Hong-Quan
Published: April 2019

As one of the most widely used artificial lift methods, electrical submersible pumps (ESPs) have been improved gradually since the 1910s. However, its performance and run life are affected by many problems such as gas lock, high viscosity fluid, corrosion, and erosion. With the development of horizontal well drilling and multistage hydraulic fracturing, sand production from unconsolidated sandstone and proppant backflow often cause severe damage to ESPs resulting in reduced operating lifespan. Measuring wear in an ESP pump and monitoring performance degradation is not only very difficult in field cases, but also in experimental studies. The results are precious for understanding the wear mechanism inside an ESP as well as guiding the ESP design and simulation. At the same time, vibration and performance data can provide significant guidance to ESP failure diagnosis, which can potentially reduce the time and cost of well service and extend ESP run life.

Wear processes inside an ESP can be classified by different modes of mechanisms. Erosive wear can be observed in the primary flow channel of the impeller (rotor) and diffuser (stator). Particle strike shroud surfaces and the scratched material is flushed away by fluids. Various semi-mechanistic erosion equations are available to be coupled with Computational Fluid Dynamics (CFD) to predict the erosion in ESPs. In the secondary flow region, balance chamber and sealing rings, particles are presented between the stator and the rotating rotor. Therefore, abrasive wear is believed to dominate the wearing process. Unlike erosion, abrasion is more complicated and abrasion equations are highly depended on geometries, physical mechanism and load between particle and target surface. In this study, a sand wear test flow-loop is designed and constructed to investigate wear in ESPs. Performance degradation, Erosion pattern, abrasion rate, and stage vibration of an ESP were recorded in a 64-hour sandy flow test.
Yanbei-Unlocking the Tight Gas Green Field Development Potential Through Integrated Technology Application
Authors: Zaini Muhamad Zaki , Du Kuifu , Zhu Ming , Feng Li Jun , Yang Hai Hua , Wei Lin , Liu Yi
Published: April 2019

Yanbei Project is a tight unconventional gas development that covers a vast area of 2,341 km2 in the Ordos basin – the largest gas producing basin in China. The paper outlines the innovative technologies applied, major achievements and the integrated approach used to successfully develop this large-scale gas greenfield of highly heterogeneous fluvial thin sands with very complicated surface terrains and resources overlaying issues (coal mines and water reservoirs). The project scope calls for drilling and fracturing 784 wells in the full field development in two phases. Phase 1 includes construction of 7 hubs, central processing facilities (CPF), and 360 km of pipelines on a complex hilly topography and aims to deliver production of 1.4 bcm/year. Phase 2 will ramp up to a higher rate. The horizontal well with multi-stage fracture development concept was introduced for the first time in the project and has significantly improved both single well productivity and project economics. More than 20 different technologies, ranging from subsurface, drilling, logging, completion, stimulation, production and facilities, have been applied each of which has been carefully assessed to ensure its value to the project. The advanced 2D seismic technologies have enabled the project to successfully reprocess and interpret a complicated 2D seismic dataset that is heavily distorted by the hilly terrains. The integration of the 2D seismic interpretation with a variety of subsurface and drilling datasets have enhanced the understanding of reservoir characterization and sandbody architectures hence significantly reduce geological risks in drilling horizontal wells in such a complex fluvial system. The drilling and surface engineering work have dealt with a variety of different challenges such as well pad acquisitions, conflicting with coal mines & surface water reservoir areas along with local community issues. One of the key success factors for the project is the integration of the industry's worldwide expertise of technologies, procedures and HSE standards coupled with the local experience, which has ensured an innovative and fit-for-purpose technology-driven solution in planning and execution of the project. The paper describes the main geological and engineering challenges and outlines an integrated approach in applying extensive but selected technologies to resolve those challenges.
Optimization of Drilling Performance Based on an Intelligent Drilling Advisory System
Authors: Abughaban Mahmoud , Alshaarawi Amjad , Meng Cui , Ji Guodong , Guo Weihong
Published: April 2019

Optimization of drilling parameters during drilling operations is a key component to obtain maximum rate of penetration (ROP) as well as minimizing the drilling cost. Advancement in computer technologies and communication are among the most important factors that can contribute to drilling optimization. In the current work, a novel rig advisory system is developed to continually improve ROP and the drilling performance. Conventionally, drillers apply drilling parameters (weight-on-bit, rotary speed and pump rate) according to past experience or to parameters specified in the drilling program. These parameters are usually kept constant over a long interval regardless of the formations being drilled. However, it is well-known that keeping constant drilling parameters to drive the bit will lead to redundant depth of cut (DOC), inducing stick-slip vibration that leads to low ROP, higher drilling specific energy (DSE), and potential damage to the bottom-hole assembly (BHA).

An intelligent drilling advisory system (IDAS), based on a soft-closed-loop solution with multiple regression analysis called optimum parameters global retrieval, has been established. Integrated with machine-learning methodology (Principal component analysis), the response of the drilling parameters with lithology changes was analyzed in real time. Additionally, the optimum control parameters direction were obtained from the gradient search and decision tree algorithms. This system monitored the relationship between the ROP and input energy delivered to the bit in real time, and calculated the optimized drilling parameters. The work presented how the IDAS procedures were applied in China, how the data was interpreted, and how optimum working parameters were obtained to guide drillers to improve drilling performance and reduce non-productive time (NPT).

IDAS has been introduced to hard formation drilling, which proved to be a success in real-time advisory aiding drillers applying proper working parameters for maximum ROP. Field applications of IDAS guidance showed significant ROP improvement compared to that of conventional drilling.

As an effective tool for further achieving the optimum DOC, a novel control system achieved satisfactory outcomes that overcome the drilling challenges in Saudi Arabia and China, which will serve as a step forward towards automated drilling operations.
Improving Imaging and Inversion Through Least-Squares Q-Kirchhoff APSDM: A Case Study from Offshore China
Authors: Jiao Chenghai , Yao Jianfeng , Teng Keat Huat , Hung Barry , Lee Jin Kyoung-Jin , Feng Huang
Published: April 2019

Least-squares migration (LSM) has become an increasingly important imaging tool in the seismic industry. It can successfully address imaging issues related to insufficient illumination and mitigate both migration artifacts and noise. More recently, a number of case studies from around the world have shown that LSM provides greatly improved seismic imaging. However, only a few examples reveal its advantages in both imaging and amplitude-versus-offset (AVO) inversion. For the amplitude aspect, compensating the effect of anelastic absorption and elastic scattering during propagation inside the earth has become increasingly popular over the past few years. The anelastic absorption and elastic scattering causes frequency-dependent amplitude decay, phase distortion, and resolution reduction. This is often quantified by the quality factor commonly called Q model. This effect can be largely compensated through Q prestack depth migration (QPSDM). Therefore, QPSDM has become an effective solution for seismic imaging in areas where strong absorption anomalies exist in the overburden. However, the excessive noise often resulting from QPSDM poses a big challenge to its application. In this paper, we propose a least-squares Q migration (LSQM) method that combines the benefits of both LSM and QPSDM to improve the amplitude fidelity and image resolution of seismic data. We also demonstrate that both seismic imaging and AVO inversions at wells can be significantly enhanced through image-domain single-iteration least-squares QPSDM Kirchhoff migration.
A Rotating Continuous Circulation Tool RCCT for Increasing Drilling Efficiency and Optimizing Borehole Cleaning
Authors: Badran Mohammed , Gooneratne Chinthaka , Ahsalan Meshari , Shaarawi Amjad
Published: April 2019

This paper presents the design, deployment and field trial test of a uniquely designed Rotating Continuous Circulation Tool (RCCT). The RCCT provides nearly continuous rotation of the pipe string and continuous circulation of fluid while making up or breaking out a new stand. Nearly continuous rotation decreases the period of static contact between the formations surrounding the pipe string and the pipe string, thus reducing the risk of the pipe becoming stuck inside the wellbore and also the wellbore collapsing. Continuous circulation results in efficient borehole cleaning. Therefore, the RCCT increases drilling efficiency and optimizes borehole cleaning. Proof-of-concept testing of the RCCT was successfully performed inside casing during a cement clean out operation, which also aided to clearly define drilling parameters required for successful operation of the tool while drilling.
Complex Geological Modeling Using Unstructured Grids: Quality Assurance Approaches and Improved Prediction
Authors: Harris Simon , Santoshini Samita , Smith Stewart , Levannier Arnaud , Khan Osama
Published: April 2019

The vast majority of grids for reservoir modeling and simulation workflows are based on pillar gridding or stairstep grid technologies. The grids are part of a feature-rich and well-established modeling workflow provided by many commercial software packages. Undesirable and significant simplifications to the gridding often arise when employing such approaches in structurally complex areas, and this will clearly lead to poor predictions from the downstream modeling.

In the classical gridding and modeling workflow, the grid is built in geological space from input horizon and fault interpretations, and the property modeling occurs in an approximated ‘depositional’ space generated from the geological space grid cells. The unstructured grids that we consider here are based on a very different workflow: a volume-based structural model is first constructed from the fault/horizon input data; a flattening (‘depositional’) mapping deforms the mesh of the structural model under mechanical and geometric constraints; the property modeling occurs in this depositional space on a regular cuboidal grid; after ‘cutting’ this grid by the geological discontinuities, the inverse depositional mapping recovers the final unstructured grid in geological space. A critical part of the depositional transformation is the improved preservation of geodetic distances and the layer-orthogonality of the grid cells.

The final grid is an accurate representation of the input structural model, and therefore the quality checking of the modeling workflow must be focused on the input data and structural model creation. We describe a variety of basic quality checking and structurally-focused tools that should be applied at this stage; these tools aim to ensure the accuracy of the depositional transformation, and consequently ensure both the quality of the generated grid and the consistent representation of the property models. A variety of quality assurance metrics applied to the depositional/geological grid geometries provide spatial measures of the ‘quality’ of the gridding and modeling workflow, and the ultimate validation of the structural quality of the input data.

Two case studies will be used to demonstrate this novel workflow for creating high-quality unstructured grids in structurally complex areas. The improved quality is validated by monitoring downstream impacts on property prediction and reservoir simulation; these improved prediction scenarios are a more accurate basis for history matching approaches.
Saving a Challenging Sidetrack Through Optimizing the Trajectory by Accurately Predicting the Fracture Gradient
Authors: Fang Zhi , Zamikhan Norshah , Huver Pieter , Ali Waznah , Ahmadiah Hanisah
Published: April 2019

Whilst drilling an exploration well through shallow depleted reservoirs, the heavily deviated intermediate hole section encountered uncontrollable losses, hole pack off, and ultimately was abandoned. A replacement sidetrack was proposed and the asset team requested an assessment of the drilling risks for the proposed trajectory. An integrated geomechanics approach was developed to analyze the fracture initiation pressures (FIP) of wellbores, which are dependent on well trajectories except on the field stresses and formation pressures. An FG model was elaborated with the integrated geomechanics approach analyzing the field data and the drilling history of the lost hole section. It predicted the FIPs of the initially proposed sidetrack trajectory with a value lower than the minimum required by the drilling team. The sidetrack trajectory was revised as instructed by the FG model analyses, which resulted in an increased FIP value slightly above the minimum required. The revised sidetrack trajectory observed minor losses with the ECD slightly exceeded the predicted FIP value during drilling, but the remaining section was successfully drilled by controlling the ECD under the predicted FIP value. If the primarily proposed sidetrack trajectory had been drilled, there could have been another lost-hole event due to the unmanageable drilling operation window. The integrated geomechanics approach eventually saved the challenging sidetrack through optimizing the trajectory by accurately predicting the FIPs.
Integrated Real-Time Pressure Monitoring Enabled the Success of Drilling a HTHP Offshore Well: A Casing Study in Ledong Area of Yinggehai Basin, South China Sea
Authors: Gao Yongde , Chen Ming , Du Chao , Wang Shiyue , Sun Dianqiang , Liu Peng , Chen Yanyan
Published: April 2019

Drilling in Ledong field at Yinggehai basin of South China Sea faces challenges of high-temperature and high-pressure (HTHP). The high pore pressure and low fracture gradient results in a narrow mud weight window, especially when drilling close to overpressured reservoir. Well LD10-C was the first exploration well targeting at reservoirs in Meishan formation. Well LD10-A and LD10-B were offset wells in a distance of 15-20km drilled for reservoirs in Huangliu formation, which is above Meishan formation. During drilling, both wells encountered severe gas kick, mud loss and did not reach target.

In order to drill and complete well LD10-C safely, a real-time pressure monitoring solution was introduced with integration technique of logging while drilling (LWD) and look-ahead vertical seismic profile (VSP). It helped to monitor pore pressure and fracture gradient while drilling and predicted top of the overpressured reservoir. This enabled to keep the mud weight and equivalent circulation density (ECD) within a safe margin to avoid kick and mud loss, helped to set casing as close as possible to the top of reservoir. The reservoir section was drilled with a manageable mud weight window.

The main achievements of this task were: 1) accurately monitor and predicted pore pressure coefficient at reservoir. The predicted pore pressure coefficient was 2.25 SG versus 2.24 SG from actual measurement. 2) accurate prediction of reservoirs top. The predicted top depth of Sand C was 2m error with accuracy of 0.05%. The top depth of Sand D was 10m error with accuracy of 0.2%. 3) 12.25in section and 8.375in section was successfully drilled deeper with pressure monitoring. The 9 5/8in casing was set 491m deeper and 7in line was set 80m deeper than plan. As a result, well LD10-C was drilled and competed without any drilling complexities.

This was first application of LWD and VSP together for pressure monitoring while drilling in Yinggehai basin. The successful completion of well LD10-C confirmed that this integrated solution was an efficient technique to predict and reduce drilling risks, optimize mud weight and casing diagram, improve operational safety and save cost in HTHP offshore drilling.
Bioclastic Limestone Reservoir Characterization of an Oilfield in the Middle East
Authors: Lin Tengfei , Wang Nai , Wang Weijun , Li Nan , Yang Shuang , Liu Yumei , Dong Junchang , Zhang Qingchun , Guo Rui
Published: April 2019

Bioclastic limestone reservoir is playing a dominant role in the petroleum industry of Middle East. The oilfield in this paper belongs to long-axis asymmetric anticline. The S formation of Cretaceous period universally developed bioclastic limestone of carbonate platform system. It is the reservoir heterogeneity that severely limits the oilfield development.

We firstly analyze the lithofacies based on the core and thin section. Then the detailed well and seismic interpretation illustrate the sequence stratigraphy and facies analysis, and tectonic evolution are analyzed to restore sedimentary procedure from Palaeocene to late Pliocene stage. Ultimately, high quality reservoir of bioclastic limestone are depicted according to comprehensive analysis.

This paper offers reference and inspiration for bioclastic limestone reservoir: reef-beach complex and sweet spots in tidal-channel are dominant reservoirs for bioclastic limestone of Middle East.
Integrated Detection of Water Production in a Highly Heterogeneous and Tight Formation Using CRM Model: A Case Study on Water Flooding Gaither Draw Unit, Wyoming, USA
Authors: Liu Kailei , Wu Xingru , Ling Kegang
Published: April 2019

Gaither Draw Unit is a heterogeneous and tight formation with an average permeability less than 0.1 mD. After more than 1.7 MMSTB water injection, there was no clear indication or benefit of the injected water from any producer. However, knowing the distribution of the injected water is critical for future well planning and quantifying the efficiency of injection. The objective of this study is to show how the Capacitance-Resistance Model (CRM) was used on this field and validated using other independent methods.

The CRM model describes the connectivity and the degree of fluid storage quantitatively between injectors and producers from production and injection rates. Rooted in material balance, signals from injectors to producers can be captured in the CRM. Using constrained nonlinear multivariable optimization techniques, the connectivity is estimated in the selected portion of the field through signal analysis on injection and production rates. In this tight formation, the whole field is divided into seven regions with one injection well and surrounding producers to conduct CRM analysis. We further use integrated but independent approaches to validate the results from CRM. The validation includes full field modeling and history match and fluid level measurement using echometering technology.

This paper focuses on a real field water flooding project in Gaither Draw Units(GDU). CRM is used to detect reservoir heterogeneity through quantifying communication between injectors and producers, and attains a production match. The fitting results of connectivity through CRM indicate permeability regional heterogeneity, which is consistent with full field modelling. The history matched full field model presents the saturation distribution showing that the majority of injected water mainly saturates the surrounding regions of injectors, and the low transmissibility slows down the pressure dissipation. Overall, the comprehensive interpretation obtained through these three independent methods is consistent, and is very useful in planning infill well drilling and future development plan for the Gaither Draw Units.

This paper shows that it is critical to integrate different sources of data in reservoir management through a field case study. The experience and observations from this asset can be applied to other tight formations being developed with water flooding projects.
Design and Evaluation of a Water-Based Drilling Fluid Formulation Using SiO and Graphene Oxide Nanoparticles for Unconventional Shales
Authors: Aramendiz Jose , Imqam Abdulmohsin. H. , Fakher Sherif M.
Published: April 2019

Unconventional shale reservoirs have become a key player in the oil and gas industry to cover the world's energy demands. Traditionally, oil-based drilling fluids (OBM) are preferred to drill shale plays due to negligible chemical interactions. Nevertheless, strict environmental regulations have motived the industry to design water-based drilling fluids (WBM) capable to control the shale-water interactions, improving their performance. Still, conventional additives are too large to plug shales’ micro-fractures and nanopores. Thus, nanoparticles due to their unique size, shape, and properties can provide a solution for the WBM. This study focus on the design and evaluation of a customized nanoparticle water-based drilling fluid (NP-WBM) using silica nanoparticles (SiO2-NPs) and graphene nanoplatelets (GNPs). The main objective is to identify the optimal NP concentration to improve the rheological and filtration properties of the NP-WBM and evaluated its inhibition benefit. The NP selection was based on the characteristics of the Woodford shale obtained through x-ray diffraction (XRD), cation exchange capacity (CEC), and scanning electron microscopy (SEM). NPs’ colloidal stability was analyzed in an alkaline environment with zeta-potential measurements. The concentration of NPs was evaluated below 1 wt.%. Laboratory measurements for the NP-WBM included API filtrate test (LTLP) and high-temperature/high-pressure (HTHP) test using a static filter press and rheological analysis with a rotational viscometer. To evaluated the inhibition benefit, the NP-WBM was tested against the Woodford shale by performing immersion and cutting dispersion tests. The results showed zeta-potential values below −30 mV for both nanomaterials, indicating good dispersibility of the NPs within the WBM. Also, significant improvements in the filtration properties were observed when adding 0.5 wt.% of SiO2-NPs with 0.25 wt.% of GNPs to the base fluid with no spurt-loss and minor effects on the rheological parameters. Higher concentrations did not show further improvements; thus the previous combination was selected as the optimal. Chemical interactions tests indicated that the Woodford shale might develop micro-fractures when exposed to water for long periods of time. However, no micro-fractures were observed when the rock was exposed to NPs. Furthermore, the NP-WBM reduced the cutting dispersion by 35.61% compared to the base fluid, showing superior inhibition properties even in high illitic shales that are prone to experience cuttings disintegration. NPs’ stability and benefits at low concentrations, indicates their potential to improve the design of WBM for unconventional shales, reducing the environmental impacts linked to the drilling operations.
Numerical Simulation and Experimental Study of Near-Wellbore Fracture Initiation Mechanism on Sandstone Coal Interbedding
Authors: Wan Liming , Chen Mian , Zhang Fengshou , Wang Li , Chen Wangang
Published: April 2019

With the development of unconventional oil and gas resources, the technology of commingling production in coal measure has been studied, which requires us to have a better understanding of the fracture near the wellbore in multi-layers. Previous studies mainly focused on the fracture morphology in a single layer and lack of 3D evolution role of microfracture propagation, so the fracture geometry in multi-layers of the coal seam and microfracture initiation near wellbore were studied in this paper.

In this study, the 3D-lattice model was used to simulate the 3D dynamic hydraulic fracture morphology near the wellbore in multi-layered coal based on XSite simulator, and the spiral perforation position was mainly studied. To verify the numerical simulation, the true tri-axial test system was implied for fracturing simulation experiments on the combination of coal, sandstone and limestone outcrops. The perforation position was changed to analyze the fracture morphology near the wellbore. Besides, the 3D scanning technology and the fracturing curve were used to study the fracture characters. As a result, the fracture morphologies near the wellbore in different perforation positions were studied.

The numerical simulation results showed that the microfracture evolution process in spiral perforation can be divided into three stages, (a) Stage 1: the vertical microfracture bands develop along the perforation hole; (b) stage 2: micro-annulus fracture forms around the wellbore; (c) stage 3: fractures break through along the perforation holes perpendicular to the minimum in-situ stress. The cleats and the natural fractures dominated the fracture initiation geometry when perforating in coal. The secondary branch fractures and the stepped fractures were the main characters in coal. Sandstone was a good barrier layer for the coal seam in fracturing, and the fracture in coal was easy to break through the limestone layer. When fracture initiated in coal layer, the fracture near the wellbore was complex with many secondary fractures, and the fracture surface was rough with poor continuity; when initiated in both sandstone and coal layers simultaneously, the main fracture developed quickly in coal and the smooth fracture surface formed near the wellbore.

The results of laboratory experiments were in good agreement with numerical simulation. The 3D evolution role of microfracture near wellbore could give a deep understanding of fracture complexity in near-wellbore area in coal. The experiments considered the actual formation combination, and the results of multi-layer fracturing could give a good guidance for field perforation optimization in the commingling of coal measure strata.
The Potential of Greenhouse Gas Emission During Flowback Process in Weiyuan Shale Production Site, China
Authors: Xue Ming , Fan Jun-xin , Weng Yi-bin , Cui Xiangyu , Li Xing-chun
Published: April 2019

Objectives/Scope: Greenhouse gas emission (carbon dioxide and methane, etc.) during shale gas production could decide whether it is a cleaner energy source than coal. However, the methane and carbon dioxide emission from flowback process during shale gas production remains unclear. The withdrawn of fracture water both from underground and surface water, and the relatively high gas pressure from the wellhead have made flowback water highly potential as a significant greenhouse gas emission source.

Methods, Procedures, Process: In this study, the estimation of greenhouse emission potential was provided based on the flowback water samples collected from shale production sites of China. The buffer capacity of carbon dioxide was estimated based on the parameters measured including temperature, pressure, conductivity, salinity, dissolved inorganic carbon (DIC), pH, chloride etc. The possible methane emission was also estimated based on the solution/dissolution curve from gas-water equilibrium during the flowback process.

Results, Observations, Conclusions: The results showed that: the relatively high salinity of the flowback water has provided a considerable buffer capacity for carbon dioxide. The water residence time in the water tank/pond largely determines air-water greenhouse flux. When the flowback water pass through the three-phase separator to the water outlet, the dissolution capacity of methane reduced sharply dropped. By switching to a higher water level in the separator, methane emission could be reduced. However, a higher water vapor ratio may be detected in the gas phase, as well. Besides the fugitive methane emission from pneumatic pumps, valves, etc., greenhouse gas emission from flowback water is a significant source which needs to be reduced in future shale gas production.

Novel/Additive Information: The determination of greenhouse gas emission from flowback could better defined the life cycle of shale gas, while provide baseline analysis for the development of greenhouse gas control technology during flowback water treatment and three-phase separator optimization.
New Low-Shock Low-Debris Gun Technology with Reliable Gunshock Simulation and Optimization
Authors: Baumann Carlos , Damm David , Escudero Jose , Smart Moises , Yang Xiang Tong , Liu Jun Yan , Wei Zhang
Published: April 2019

Many high-pressure/high-temperature (HP/HT) gas fields are developed in Northeast China with wells that have pressures reaching 20,000 psi and temperatures up to 180°C. The main difficulty in perforating these wells is the high wellbore pressure, which leads to large gunshock loads when the guns fire. Field operators experienced substantial losses when perforating these HP wells with standard guns; therefore, they needed to minimize the risk of equipment damage due to gunshock and reduce the amount of perforating debris left in the well.

To reduce gunshock loads and perforating debris problems, a new low perforating shock and debris (LPSD) gun system was developed specifically for HP/HT wells. Compared with standard guns, LPSD guns produce much less gunshock and negligible amounts of debris; thus, by using LPSD guns operators can minimize gunshock risk and save on cleanup runs. LPSD guns leave almost no debris in the well because LPSD guns retain all the metallic components inside the gun carriers, including the shaped charge cases, which remain virtually intact inside the guns. Complementing the new LPSD gun technology, we use gunshock simulation for shock load reduction and optimization. These are key elements of the perforating job design, and they are critical to prevent equipment damage in HP wells.

We show several examples of tool damage resulting from gunshock loads when third-party guns were used. These gunshock problems represented costly losses from equipment damage and nonproductive time. Using gunshock simulation, we show the origin of shock loads and the magnitude of the loads acting on the equipment, resulting in collapsed casing, corkscrewed tubing, and damage to packer mandrels and seals. We compared the performance of LPSD with standard guns under the same perforating conditions, demonstrating that LPSD guns can reduce shock loads significantly, making LPSD guns better suited for all HP wells, including those in Northeast China.

The LPSD gun system developed for HP wells significantly reduces the amplitude of the transient pressure waves and associated gunshock loads, and totally reduces the amount of debris. The reduction of gunshock enables perforating wells that otherwise cannot be safely and reliably perforated with standard equipment.
Prediction Methods of Key Development Indexes of Large Gas Fields Based on Big Data Analysis
Authors: Yuping Sun , Chunxiao Guan , Jingping Zhang , Qiaojing Li , Jialiang Lu , Hongjun Tang , Weijun Shen , Haibo Li , Hewen Zhang
Published: April 2019

Large gas fields play an important role in natural gas industry. Recovery rate, plateau duration, recovery at the end of plateau, decline rate and recovery factor are the key development indexes for dynamic performance analysis and development planning. Scientific prediction for those indexes can support gas development planning strongly.

Through mining statistical analysis of 150 large gas fields and numerical simulation analysis, 23 objective influencing factors which affect the development effect are studied. Gas fields are classified according to the main influencing factors, and then the distribution of development indexes are summarized. Finally, a series of prediction methods for key development indexes are established.

Based on the above work, it is found that matrix permeability, drive types, reservoir architecture and fluid type are the most sensitive factors among them. According to the most sensitive factors, gas fields should be divided into 4 categories, and 13 subcategories and the distributions rules of development indexes of all categories are presented. Then new prediction methods for development indexes are established, including linear empirical formula method, similarity analogy prediction method based on Euclidean theorems, and probabilistic values method. In this process, according to the characteristics of influencing factors, logarithmic and piecewise function methods are used for dimensionless treatment, and the prediction accuracy of the methods is improved. Finally, the expert system software is developed which can automatically predict the key development indexes. The prediction accuracy is over 80% which can satisfy the requirement of strategic planning.

The new methods have the characteristics of multiple methods, applicable to multiple gas field types and predicting multiple development indexes. Those methods can be applied to predict the development indexes of new fields and evaluate the development effects of matured gas fields in batch.