bluuebunny/crossref_metadata_2025 huggingface dataset:
Multi-Component While Drilling MCWD Resistivity Inversion for Thin Carbonate Reservoirs
Authors: Larbi Zeghlache Mohamed , Mumtaz Asim , Ferreira Enrico
Published: April 2019

To maximize reservoir contact during well placement in layered carbonate reservoirs, reentry and newly drilled wells often target a specific layer. In this case, traditional well placement techniques of horizontal wells using a reactive or semi-proactive approach result in repeated exits of the reservoir target into the cap rock or potentially dip out of the target zone. This environment may result in losing reservoir footage, a lower net-to-gross, prolonged drilling time and wellbore challenges. All these items increase wellbore delivery time and cost.

Existing logging-while-drilling (LWD) technology for well placement and formation evaluation has been extensively used in different environments. For example, borehole resistivity image logs to acquire real-time formation dips and provide at-bit resistivity measurements to help identify local features that may correlate with the structural dip. However, in many cases, especially for wells drilled close to the flank, carbonate layers are not as "flat" as seen in the seismic sections.

Conventional deep-azimuthal resistivity technology was designed and introduced mainly for a clastics environment, where a clear resistivity contrast between shale and sand zones exists. The technology can help in mapping the target sand beyond the well trajectory. This is not the case with carbonate reservoirs, where the contrast is not obvious and the signal saturates due to proximity to anhydrite layers, masking the different reservoir layer boundaries. To overcome this challenge and enable bed boundary mapping tools to focus on a shallow depth of investigation, a new resistivity inversion called multi-component while drilling (MCWD) is introduced.

The MCWD inversion technique utilizes the deep-azimuthal resistivity data to map the thickness and boundaries of different resistivity layers focused within the required depth of investigation. Consequently, conventional deep-azimuthal resistivity technology is adapted for proactive geosteering in relatively conductive medium by mapping the high-resistivity layer boundary (anhydrite) and the low-resistivity contrast base layer to maintain the wellbore optimally in the target zone.

Results of this new inversion are demonstrated to show the combination of deep-azimuthal resistivity technology along with MCWD inversion to successfully place horizontal laterals within carbonate sublayer. Another added value is the mapped structural features that can help to improve the structure model and assist with real-time geosteering decisions. In addition, qualitative petrophysical evaluation could help to map the water front and the oil/water contact in some cases.

The deployment of this technology has helped to improve drastically the Net-to-Gross (N/G) in these challenging environments, and more applications are currently being studied to develop further the use of the real-time azimuthal directional resistivity logging data.
Potential and Risk Analysis of Offshore Fractured Light Reservoir
Authors: Shi Hongfu , Yue Baolin , Luo Xianbo , Shi Fei , Xiao Bo
Published: April 2019

The exploration and development of offshore oilfield facing unprecedented challenges include the decline in the quality of oil reserves, increase of invest and strict environmental protection policies. Usually, low permeability reservoir, heavy oil reservoir complex fault block and small reservoir located far from an existing facility are classified into marginal oilfield. More and more marginal oilfield is put on the schedule of development. In the view of economic, The internal rate of marginal oilfield return is lower than the benchmark rate of return of the industry, but higher than the cost discount rate of the industry. An integrated work flow is presented to improve the tap the potential and mitigate the risk of marginal oilfield involved in dependent development of small oilfields, unit exploitation of small oilfield group, simple platform, extended reach well and phased development. The LD oil field is taken as an example to state the strategy of marginal oilfield.
Unique Data Standardization Challenges and Solutions: Raw and Basic Processed Microseismic Data
Authors: Al-Thani Lulwah , Al-Naim Rand , Al-Zayer Ali , Bin Mahfoodh Abdulelah
Published: April 2019

Microseismic monitoring of multi-stage hydraulic fracturing has emerged as a key technology for unconventional stimulation wells to show the 3D propagation of the induced fractures. Monitoring the dynamic growth of these fractures gives insight into the quality of the completion design as well as better understanding of reservoir characteristics and rock properties.

The lack of industry standard format for microseismic data resulted in major challenges on different aspects of transmission, interpretation and archiving. This has raised the need to establish a standard format for both raw and basic processed microseismic data.

Basic processed data for each microseismic event is processed remotely in the field and transmitted in near real-time to central offices to be mapped and integrated with other data types using specialized technologies to enable timely decision making. Data should contain the minimum and sufficient information to characterize and indicate the location and magnitude of the induced fractures.

Raw microseismic files are large in size and typically delivered to data proponent in external storage devices at the end of the hydraulic fracturing operation. These files should contain additional attributes collected at the field for all microseismic events and stages such as trace header description, geophone orientation and specification. Both basic processed and raw microseismic data must be captured in a standard format to be stored in a corporate database to safeguard company assets, ensure data integrity and availability for future operations.

Data standardization for both basic processed and raw microseismic was developed by compiling the minimum data requirements from subject matter experts. The new standard for basic processed data consists of a vendor-neutral format that is suitable for all service companies and compatible with major interpretation and visualization technologies. This standard mainly focuses on setting guidelines for microseismic events location and magnitude. Raw microseismic files are in "SEGY" format that include additional meta data attributes such as frac stage number, treatment and monitoring well.

Solutions used to address current microseismic data exchange challenges went beyond data standardization to include modification of existing real-time data transmission system, interpretation technologies and database schema to accommodate and visualize microseismic data at different stages.

Future challenges of microseismic will include the need for technology and data transformation to adopt new generation processing technologies and algorithms to enable on-site data analytics and huge data transmission. This new approach will automate filtering signal from noise to streamline real-time signal transmission and ensure integrity. This session will focus on highlighting microseismic current and future data challenges including discussions on some of the proposed solutions.
Integrated Multiple Parameters Method for Candidate Selection in Refracturing Treatment
Authors: Lu Mingjing , Su Yuliang , Wang Wendong , Zhang Ge
Published: April 2019

Refracturing treatment are performed since stimulation effect won't last for entire life. Screening wells for refracturing needs a systematic analysis of huge amounts of data. With literature review, it is obviously that there are many factors controlling the success of refracturing and factors may vary in different oilfields. Proper factors and data processing are the primary principle in candidate selection. The Integrated Multiple Parameters (IMP) method is presented to provide assists in selecting candidate wells.

After deeply researching over 200 restimulated wells, all factors thought to be related with success of refracturing are listed and analyzed, results show that single factor may have great influence on restimulation but no significant patterns can be obtained since too many factors making things complicated. The IMP method proposes five parameters which are all integrated by those single factors. It is emphasized that all parameters have physical or engineering meanings which makes it easier to quantify their correlation in refracturing. Besides, all the parameters are dimensionless which makes it easier for using in mathematical models and statistical analysis.

The five dimensionless parameters are developed considering the most important aspects of candidate wells selection which are showed as followed: fracture reorientation, well completion, reservoir depletion, production decline, oil-water well connectivity. Parameters are calculated for all the restimulated wells to dig into their correlation with the outcomes of refracturing. A simple decision model is built to help with screening wells for refracturing. Results shows that it is more executable to evaluate and predict the success of refracturing with these dimensionless parameters. Fracture reorientation parameter is the primary one to be considered since it leads to fracture reorientation which brings significant production increment. Then two types of potential wells are picked: (a) wells with dissatisfied initial well completion, low production decline rate and high oil-water connectivity parameter; (b) wells with satisfied initial well completion, high well completion parameter, low production decline parameter, reservoir depletion parameter and low oil-water connectivity parameter for wells that are not easy for fracture reorientation. Wells selected are proved to be refracturing potential which verify the reliability and accuracy of IMP method.

The IMP method is an improved approach integrating most of the important factors which makes candidate selection much more predictable and it succeeds in screening out more than 80% of the potential wells in field test. Also, it can be applied widely in different oilfields since all the parameters are dimensionless. By combining with some mathematical methods such as neural networks, it can even predict increment of the restimulation treatment.
An Integrated Modelling Workflow to Optimise Initial Production Rate and Well Spacing for Longmaxi Shale Gas Play
Authors: Yong Rui , Zhuang Xiangqi , Wu Jianfa , Wen Heng , Shi Xuewen
Published: April 2019

Ning201 Longmaxi shale gas play is located on the southwest edge of Sichuan Basin. Block Ning201 surface is very mountainous and elevation range of drilling pads is between 400 meters and 1300 meters. The target layer of shale gas exploration and development is mainly the Wufeng Formation of the Ordovician system and the organic-rich shale interval of the Lower Longxixi Formation of the Silurian system. The total thickness is between 30m and 50m, and the overall buried depth is 2300~3200m. Field development of Ning201 shale gas play was geared up in 2014. During early appraisal phase before 2014, average testing results of wells were 10~15×104 m3/d. 7 vertical appraisal wells and 50 horizontal wells have been drilled and 38 horizontal wells among them have been put into production to evaluate optimized development strategy until middle of 2017. Changning area accomplished the construction of 15×108 m3/a production capacity. During production appraisal phase, different well spacing pads were configured, and some cross-well interference testing were performed to determine optimal spacing in Ning201 block. Only qualitatively understanding can be achieved with spontaneous field efforts and quantitative evaluation of long-term impacts on production with varying initial rate control and well spacing is still missing.

In this paper, an integrated modeling workflow was introduced to accurately simulate the production behavior of a representative shale gas well and to control production through a calibration model to optimize well spacing and maximize economic returns. The workflow begins with microseismic monitoring during shale gas well fracturing operations. Considering the fracturing pumping procedure, fluid and proppant volume and subsurface features, including formation, natural fractures and in-situ stresses, the heterogeneity of the hydraulic fracturing system propagation ensures that the simulated complex hydraulic fracturing network is in line with reality. After establishing a detailed hydraulic fracturing model, production performance is matched to history to better calibrate the conductivity of hydraulic fracture network in dynamic model as a relaible predicting tool.
Compositional Variation of Natural Gas in Kerogen During Production
Authors: Pang Wei , Akkutlu I. Yucel , Ding Shidong , Zhang Tongyi , Xia Wenwu
Published: April 2019

Organic matter in source rocks such as coal and shale hold significant amount of adsorbed gas. Laboratory methos are available to measure the gas amount stored in the source rock samples. However, adsorbed gas release from the organic pore network and its production using wells is an issue under debate. The intricacy in the debate is mainly due to the physical properties of the adsorbed phase adsorbed phase. The adsorbed phase has an unknown composition and its molecules released in a selective fashion controlled by the organic pore walls. The organic matter nanopores bring in added complexity to the analysis due to nano-confinement effects. Our objective in this study is to predict the gas composition in kerogen pores in order to gain insight into the compositional variation with the pore size distribution in the formation. This prediction should be done properly at the initial conditions and during the pressure depletion. Thus, we also would like to investigate gas desorption impact on the adsorbed hase composition due to production.

A molecular simulation method is developed using grand canonicalMonte Carlo simulation to study the in-situ composition of natural gas in model matter pores. We used the composition of produced fluid from a Chinese shale gas well. In essence, the method redistributes the fluid composition back into the organic pores at initial reservoir conditions. Then one-by-one the pores are depleted while the compositional variation in the pores is monitored. The recovery is measured by comparing the residual hydrocarbon molecules at different pressure steps during the depletion. The mean free path length of the fluid molecules, the fluid density and viscosity are computed once the thermodynamic simulation reaches an equilibrium.
Geomechanical Anisotropic Method Increased Fracturing Efficiency in Tight Oil Production: A Case Study of Yanchang Formation, Ordos Basin
Authors: Xi Shengli , Hou Yuting , Li Xianwen , Hu Xifeng , Liu Peng , Zhao Xianran
Published: April 2019

The Triassic Yanchang formation is rich in tight oil resource at Ordos Basin. The oil sandstone and oil shale of Chang 7 member are widely spread in the basin and have huge potential in oil production. Due to low porosity and low permeability, producing oil from tight oil reservoir depends on hydraulic fracturing. A successful hydraulic fracture requires accurate estimations of horizontal stresses and rock elastic properties in design and operation.

Chang 7-2 is shale and sandstone interbed reservoir and Chang 7-3 is shale oil reservoir with lamination sedimentary structure. The rocks with lamination structure are very anisotropic, and it needs to be considered in computation of horizontal stresses and rock elastic properties.

In this paper, we present a case study to illustrate the advantages of anisotropic geomechanics model. Anisotropic horizontal stresses and rock elastic properties were calculated and used in hydraulic fracturing design. The perforation intervals were selected at depths with low stress magnitude based on stress profile. The perforations efficiency was analyzed, and perforation interval with low efficiency was removed. Major stimulation operation parameters, total volume, proppant volume and slurry rate, were optimized with anisotropic geomechanics model. Fracturing operation results showed that the total volume was decreased by 16.5%, proppant pumped increased by 11.4% and daily oil production increased by 73.7%. This case study demonstrated that anisotropic geomechanics model help to improve operation efficiency and increase oil production.
Modeling and Experiments for CO2 Blowdown from the Cryogenic Pilot Plant and the Mitigations Measure
Authors: Surmi Amiza
Published: April 2019

A pilot of cryogenic distillation technology is designed and installed for separation of the high CO2 concentration of feed up to 80 mol % from natural gas. However, the main concern was the dry ice formation during depressurization or blowdown might cause the pipeline and equipment blockage and consequently resulting in safety issues.

A dynamics simulation and modeling were conducted using commercialize software to determine the settle out temperature during the blowdown especially emergency condition. The investigations were focused on the high operating pressure and low operating temperature with a high CO2 composition which is closer to transient condition and solid region. Then, more comprehensive modeling was conducted by incorporating the equipment and piping design data including the sizing of relieve valves (RVs) and blowdown valves (BDVs). The accuracy of information is very crucial to obtain more reliable results.

It was observed that at high operating pressure, (50 to 75 barg) and low operating temperature,(-58 to 15 °C) the settle out temperature due Joule-Thomson (JT) effect were −58 °C and −92 °C for 60% and 80% CO2 concentration, respectively. Based on the phase diagram, in this condition, the CO2 will be under a solid region. As a result, the Minimum Design Metal Temperature (MDMT) of −100 °C was selected for equipment and pipelines design to avoid material brittle-fracture. Few mitigations measure were designed and installed to avoid the CO2 solidification. The BDVs were installed at the warmer area to minimize the JT effect leading to lower operating temperature than CO2 solidification temperature resulting to potential equipment blockage. The electrical heat tracings were installed at the outlet flange and outlet line of RVs and BDVs to maintain fluid temperature above CO2 solidification limit. This is to prevent CO2 solid from attaching to the pipe wall and build up in the piping in the event of relief. Another mitigation was by installing the outlet line with sloped toward vent header and free from instrument probe or sensor to prevent CO2 solid from build up at piping dead leg section. As a result, no sign of CO2 solid found in the sections that equipped with mitigations measure during experiments.

An inherently safer design of equipment and pipelines are very crucial especially for high CO2 concentration, high operating pressure and low operating temperature with the appropriate mitigations to avoid catastrophic failure.
Evaluation of Dynamic Reserves in Ultra-Deep Naturally Fractured Tight Sandstone Gas Reservoirs
Authors: Luo Ruilan , Yu Jichen , Wan Yujin , Liu Xiaohua , Zhang Lin , Mei Qingyan , Zhao Yi , Chen Yingli
Published: April 2019

Ultra-deep naturally fractured tight sandstone gas reservoirs have the characteristics of tight matrix, natural fractures development, strong heterogeneity and complex gas-water relations. There is strong uncertainty of gas reserves estimation in the early stage for such reservoirs, which brings big challenge to the development design of gas fields. Taking Keshen gas field in Tarim basin as example, during the early development stage, the dynamic reserves were much less than those of proven geologic reserves. As results, the actual production performances are obviously different from those of conceptual design. What are the reasons? How to adjust the development program of gas field? Based on special core analysis, production performance analysis, gas reservoir engineering method, and numerical simulations, influencing factors on evaluation of dynamic reserves for ultra-deep fractured tight sanstone gas reservoirs are analyzed. The results show that rock pore compressibility, recovery percent of gas reserves, gas supply capacity of matrix rock, water invasion are the major factors affecting the evaluation of dynamic reserves. On the basis of above analysis, some suggestions are given for the evaluation of dynamic reserves in Ultra-deep fractured tight sandstone gas reservoirs. For this kind of reservoirs, it is reasonable to determine the gas production scale based on dynamic reserves instead of proven geological reserves.
A DNN Trained to Pick Faults in Seismic Data: Implementation and Results
Authors: Montaron Bernard , Montaron Francois , Montaron Renaud
Published: April 2019

A software system based on deep neural network (DNN) technology was designed and trained to recognize fault lines in 2D seismic vertical sections, and fault surfaces in 3D seismic cubes. The system was successfully tested on public domain data from several basins in New Zealand. The paper describes the key components of the system and explains how they were designed. A relatively small size window is used to scan 2D seismic sections. Two DNNs identify if the window contains a fault and output the vector corresponding to the fault segment in the window. After scanning the entire section, a clustering algorithm is applied to group these vectors in separate clusters corresponding to the faults in the section. Finally, a linear regression algorithm calculates the fault lines – not always straight – in the section. Fault lines in successive 2D vertical sections of a 3D cube are associated to form fault surfaces. The training data set that was created to train the DNNs contains 120,000 examples. The validation test set has 30,000 examples. A special workflow and software were developed to generate these 150,000 labelled examples with a mix of synthetic and real data. The results obtained are quite satisfactory: the success rate exceeds 95% on the validation test set. The vector clustering algorithm properly handles crossing faults. The system is designed to quickly learn to correct mistakes highlighted by geophysicists, like patterns wrongly identified as faults, or missed faults. This system was trained to identify fault patterns in seismic data just based on examples. The concept can easily be expanded to recognize many other types of patterns such as structural or stratigraphic traps, horizons, and types of seismic facies. This fault detection software is the first step toward a machine learning-based system for automated structural interpretation of seismic data.
Well Stimulation Evaluation in Horizontal Wells with Emphasis on Petrophysics and Rock Mechanics: A Case Study in Deep, Tight Carbonate Formation
Authors: Zhou Yuhai , Zhang Wenyu , Zhu Ding
Published: April 2019

Tight carbonate formations with extremely low porosity and permeability depend on well-designed completion and stimulation treatments to achieve economic production. Acid fracturing, a relative cost-effective choice compared with propped fracturing, is widely used for carbonate stimulation. However, many factors contribute to the acid etching created conductivity, which is a key parameter for the success of acid fracturing. From a petrophysical perspective, depth-by-depth rock mechanical properties, stress distribution as well as the heterogeneous petrophysical properties (e.g. porosity and permeability) are important local information affecting final fracture conductivity. In this paper, we conduct an integrated evaluation for multi-stage acid fracturing in a horizontal well in a deep, tight carbonate reservoir in Tarim field, China.

We perform multi-mineral analysis and estimate volumetric concentrations of minerals, porosity, and fluid saturations with conventional well logs. Since shear wave sonic logs are not available for most of the wells, we estimate rock mechanical properties (Young's modulus and Poisson's ratio) using effective medium models including self-consistent approximation and differential effective medium theory. Corrections including the impact of fluids are developed using Gassmann's fluid substitution. Besides, we estimate depth by depth permeability with empirical correlations. Core measurements are used for cross-validating the well-log-based estimates of rock mechanical properties, porosity and permeability. Horizontal stress distribution and closure stress field are generated using poroelasticity stress model with estimated Young's modulus and Poisson's ratio as inputs. We also perform variogram analysis on well-log-based estimates of permeability and obtain its correlation length in both vertical and horizontal direction to quantify formation heterogeneity.

The estimated rock mechanical properties, stress distribution, and petrophysical properties are used as inputs to 3D acid fracturing treatment modeling. The simulated fracture geometry, especially fracture height, is highly dependent on stress variation. The modeled acid transportation in fracture is strongly affected by permeability correlation lengths. The study result shows that the conductivity created by acid fracturing under local high closure stress is insufficient for successful acid stimulation treatments.
Environmental Impact Study and Experience Sharing of Produced Water Reinjection from Unconventional Gas Development
Authors: Chen Changzhao , Li Xingchun , Wu Baichun , Zhang Kunfeng , Song Quanwei
Published: April 2019

The world has seen a peak in unconventional gas development in recent years. Based on the practice of unconventional gas field development domestic in China and abroad, it is risky that the reinjection water may contaminate groundwater in local or adjacent areas during reinjected fluid migration. Ensuring environmental safety of the reinjection is a multi-disciplinary system project. This paper carries out the analysis and shares the experience of China's practice based on the actual cases from the following aspects. 1) The screening of the well location and the formation of the reinjection. 2) The drilling and cementing construction of the reinjection well, which considers the factors such as cementing quality and cement height and casing material. 3) The estimation of the total reinjection capacity, and the factors such as porosity and permeability of the geologic trap and reservoir fracture pressure is considered. 4) The monitoring of well and migration of reinjection fluids. Further environmental risk study of produced water reinjection is presented in this paper, on both sandstone formation of tight sand gas field and carbonate karst formation of shale gas field in China's typical unconventional gas development areas, using laboratory geochemistry experiments and large area geophysical test to obtain seismic data.
Unlocking Marginal Deep Water Fields Development through Reservoir to Surface Integrated Asset Modelling
Authors: Marmier Remy , Ajiboye Ajibola , Berson François , Darde Mathieu , Houdbert Vincent
Published: April 2019

Development of marginal deep water fields requires an integrated and cost-effective approach for costs minimization and production enhancement by synergies with existing surrounding infrastructures. This paper details the successful use of Integrated Reservoir and Production Modelling to unlock the development of three marginal deep water oil discoveries in synergy with an existing surrounding subsea development. A marginal field is usually defined as a field that may not produce enough net income to make it worth developing. Deep water satellites are among those, requiring important development optimizations to unlock their potential. Integrated Reservoir and Production Modelling is largely used within the Oil and Gas industry for evaluating production forecasts associated to development assumptions by modeling the fluid flow from pore to process while honoring all required subsurface to surface constraints. This paper describes how the use of such modeling approach has been used to unlock the development of these marginal oil discoveries by evaluating the value of different development concepts from stand-alone to tie-back together with standardized and under-qualification subsea technologies. The Integrated Reservoir and Production Models were made of the three reservoir dynamic models of the three marginal fields connected to the well and network production models capturing the various concepts evaluated. Three main development concepts have been tested: stand-alone, short tie-back to field X and long tie-back to field Y. For all these concepts, many sensitivities have been performed: well implementation patterns, well completion and activation, production and injection networks design including subsea boosting and surface capacities debottlenecking. Tie-back to field X has then been further evaluated to determine detailed bases of design maximizing the value of the project. Integrated Reservoir and Production Modelling has been key to enable cross-functional team work and determine the best incremental value of these marginal fields in synergy with the production of the surrounding existing field.
Real-Time Interpretation of Supercharged Formations during Pore Pressure Monitoring
Authors: Paul Scott , Garcia Mayans Aldrick , Patel Nikhil , Blyth Matthew , Rodrigues Anthony
Published: April 2019

The basic objective of real-time pore pressure (RTPP) services is to maintain the equivalent static density (ESD) and equivalent circulating density (ECD) within a desired mud weight (MW) window. This paper will present a new workflow to differentiate between supercharging in low-permeability, limited lateral extent sands, and genuine elevated pore pressure; ultimately preventing unwarranted MW increases that might either result in premature termination of the section or induce losses.

In a typical workflow, log-derived models are used to compute the pore pressure (PP) in shales. These models are calibrated with drilling events and prompt formation pressure-while-drilling (FPWD) pretests in sands. However, in the Gulf of Mexico (GoM), sub seismic sand lenses are susceptible to supercharging; sometimes manifesting as an event gas peak. Moreover, using these gas events to determine supercharging have proven unreliable as they do not systematically occur. A novel workflow using time-lapse FPWD measurements, incorporating the acquisition environment, and the ability to circulate drilling mud at different flowrates to iteratively demonstrate the presence of supercharging has been developed.

A common scenario is presented from a deep water well in the GoM in which both RTPP and FPWD services were run. As drilling progressed, the shale PP computed from the sonic logging-while-drilling tool was repeatedly validated with FPWD measurements. However, then a pretest conducted across an underlying sand showed PP value slightly higher than the computed shale PP. Based on conventional methodology, this condition would trigger a MW increase. Following regulatory requirements, ESD should be in a specified range above the confirmed PP. If the MW was increased further, the resulting ECD would be near the last casing shoe leak off test value, compromising wellbore integrity. If the flow rate was reduced to control the ECD, then wellbore cleaning would be compromised. A departure from the previously observed sand-shale PP equilibrium was unexpected and supercharging was suspected in this underlying sand. Clear evidence of supercharging was demonstrated by employing an iterative sequence of four repeated pretests with parameter adjustments. Experimental data were obtained and showed that no MW increase was required. Based on these results, the RTPP model was adjusted accordingly, and drilling continued without any problems to the planned section total depth.

The presence of potentially supercharged sub seismic sand lenses complicates PP calibration. This new workflow is proposed to identify supercharging in these sands; thus, minimizing unwarranted MW increases, which could either result in premature termination of the section or induce losses. Either of these results could lead to operation cost overruns and extra casing and liner runs. The efficiency of the new workflow is demonstrated by the safe and successful drilling of a Deepwater prospect.
Disclose Hidden Hydrocarbon HC Reserves from Additional Zone of Interest AZIs Using dT LogR Method in Lunar Field, Gulf of Thailand
Authors: Kamkong Paphitchaya , Karnjanamuntana Thamaporn , Prungkwanmuang Weera , Yingyuen Jakkrich , Oatwaree Dejasarn , Amornpiyapong Nichakorn , Khositchaisri Patcharin , Tivayanonda Vartit , Wongsuvapich Dutkamon , Tongsuk Soraya
Published: April 2019

Lunar field is a marginal gas field located in the Gulf of Thailand. A significant portion of reservoir sands is currently categorized as Additional Zones of Interest (AZI) which is not accounted in reserves. As for this kind of sand, the conventional petrophysical evaluation alone cannot certainly distinguish between hydrocarbon and water in the porous medium. The alternative method (dT LogR) for formation re-evaluation is therefore considered in attempt to reduce uncertainty in fluid classification and reveal hidden hydrocarbon potential from these AZIs.

There are 2 phases in verifying the validity of dT LogR method. Phase I: dT logR method (Ref. Q.R. Passey et al., AAPG 1990) was tested against the unperforated AZI sands of 10 selected platforms in order to fine-tune scaling parameters in dT logR. The total of 12 gas-potential AZI candidates were selected for perforation test. Data acquisition was also planned to obtain the reservoir deliverability information in order to further calibrate the interpretation model. The production test results of these sands showed that the accuracy of the interpretation was 41% (5 sands of 12 candidates produced gas) but 33% (4 sands of 12 candidates) showed water flow.

Phase II: The production test data from perforated AZIs in phase I and the well correlation were then incorporated in dT LogR assisted log reinterpretation. Additional 13 gas-potential AZI candidates were identified for 2nd perforation test to prove the correctness of the recalibrated petrophysical model. The results showed success in model improvement of which its accuracy increased to 61% and no high water production was observed in any of them.

After using dT LogR method to assist petrophysical evaluation, a total of 469 metres of unperforated AZIs were reconsidered to be productive gas bearing formation. In other words, 22 BCF of gas reserves and 873 MSTB of condensate reserves from these upgraded AZIs were added. In addition, it is foreseen that the remaining AZIs of other platforms are to be further reevaluated and therefore improves the confidence in reserves booking and field development planning of Lunar Field.

In conclusion, the dT LogR method is a very useful tool for Lunar Field to significantly reduce uncertainty of fluid classification which in turn provides lots of benefits in gas field management adding immeasurable value to Lunar Field.
Study on the Brittleness Evaluation in the Naturally Fractured Carbonate Formation and Its Application in the Ordos Basin
Authors: Ma Xinxing , Kao Jiawei , Zhou Zhou
Published: April 2019

Rock brittleness is a key factor to influence the fracture behavior in the formation. Therefore, it is important to evaluate the brittleness when doing the hydraulic fracturing. Previous studies provided various methods for rock brittleness evaluation. Few evaluations, however, could be applied for the naturally fractured carbonate formation because those methods did not integrate the influence from lithology, natural fractures and vugs. Hence, this paper indicated an integration evaluation method to investigate the brittleness in the naturally fractured carbonate formation.

The rock in this study was from the formation in the Ordos Basin. The brittleness evaluation method asked the experiment studies that included triaxial compression test, continuous strength test, Kaiser test and X-Ray Diffraction analyze. Based on the results, the influence of substrate properties and fractures-vugs in fractured carbonate rock are analyzed. Then a method to evaluate the brittleness of fractured carbonate rock is raised in which the stress-strain curves of rock mechanics tests, geologic microcharacter and the characteristics of fractures are considered. The method can give a better application in Ordos Basin.

The results show that the failure mode of fractured carbonate rock under the effect of confining pressure is mainly the shear failure. The facture will have an obvious effect on the strength of rock. The brittleness of fractured carbonate rock appears as the ability for resisting inelastic deformation before rupture and losing rate of bearing capacity after rupture, besides the minerals of rock and the development of fracture will influence the brittleness. With the increasing of confining pressure, the fractures tend to be closed which leads to the increasing of brittleness. However, the carbonate in high confining pressure is characterized by plasticity, the brittleness would reduce. The brittleness was used to design hydraulic fracturing work in the naturally fractured carbonate formation of Ordos Basin.

Hydraulic fracturing is necessary to guarantee a successful development in the naturally fractured carbonate formation. Therefore, the brittleness evaluation method is worth to study when designing the hydraulic fracturing.
The Study and Application of Intelligent Thixotropic Cement Slurry Based on Nanotechnology
Authors: Lu Haichuan , Zheng Huikai , Li Zongyao , Feng Wangsheng , Tang Shaobing , Zou Jianlong , Li Lirong , Tan Wenli
Published: April 2019

Lost circulation and fluid channeling in cementing process are common technical problems in domestic and overseas oil-gas field, and making huge damage to oil-gas field development. The cement sheath is easy to be broken because it has only little deformation under force which will affect the cement long-term packing property that could ensure the oil and gas production go smoothly. Aiming at the above problems, to conquer the shortage of traditional materials, a new multi-functional material is developed by combining nanotechnology and polymer synthesis technology according to microstructure design principle. And then an intelligent thixotropic cement slurry system is built. The novel intelligent thixotropic cement slurry is able to rapidly respond to the external stimulus of shear force due to the dynamic net structure between the nanometer material and the polymer. It is thin under shear and become thick rapidly when it is still and become thin again after shear. The process is reversible. The new system which conquers the problems existing in the conventional thixotropic cement slurry could not only make full use of its functions but also reduce the construction risk. The experiments show that the cement slurry has strong thixotropy unaffected by temperature and short transition time and can prevent lost circulation and fluid channeling in cementing process. And the cement stone with the multi-functional material has well tenacity and excellent ability of resisting damage which could keep long-term packing property. Besides, the thixotropic mechanism of nanometer material and its function on mechanical property improvement are studied in the point of microstructure, which will lay a certain foundation for the application of nanotechnology in well cementing. The intelligent thixotropic cement slurry have been used successfully in many oil fields, which prove its function on solving the problems of fluid channeling and lost circulation.
Advanced Study of Pore Structure and Mechanical Property Change of Tight Sand Due to Thermochemical Treatment
Authors: Al-Nakhli Ayman , Mahmoud Mohamed , Al-Badairy Hameed , Alqam Mohammed
Published: April 2019

The demand for unconventional gas is rapidly increasing to provide enough energy to maintain sustainable growth for industrial countries. Even oil producers can develop UG to be directed to internal industrial and power consumptions. As Unconventional gas reservoirs are located in deep high-stress formations, one of the critical challenges gas producers are facing is to develop a cost effective stimulation method that can reduce production cost to lower than Break-even.

In this paper a novel stimulation method, based on thermochemicals, is introduced. Thermochemicals when injected in tight reservoirs generate localized pressure-pulses, which result in creating microfractures, improve permeability and increase stimulated reservoir volume (SRV). Tight core samples were treated with thermochemicals and the impact on mechanical properties were studied. Generated localized pressure was clearly detected during Coreflood treatment. Microstructural and mineralogical properties were also investigated using microscopy and spectroscopy. CT-scan, micro CT-Scan, Young's modulus, Poisson's ratio and ultrasonic velocities were measured pre and post treatment. Results showed creation of fractures and microfractures, which resulted in improved rock conductivity.

Results show that, micro-factures are created inside the used sample due to the in-situ generation of heat and pressure. The density of those micro-factures is strong function of the chemical concentration and the injected volume. Creation of micro-factures leads to improve the formation conductivity and reduce the capillary forces, therefore, enhances the hydrocarbon recovery. The outcome of this study is to understand the impact of thermochemical treatment on rock integrity. The ultimate objective is to establish a relationship between the injected chemicals and the alterations of formation properties such as permeability and porosity. This work will serve as a baseline for designing and conducting thermochemical operations for hydrocarbon reservoirs.

In this study a novel stimulation technique to increase stimulated reservoir volume (SRV) is presented. In basins with excessive tectonic stresses, the current novel treatment can become an enabler to deeply stimulate well stages which otherwise left untreated. A new methodology is developed to lower fracturing cost and increase unconventional gas production. A better connectivity reduces the required number of hydraulic fracturing-stages.
Shaped Memory Polymer: An Innovative Approach to Sand Control Open Hole Completion in Thin, Multilayered, Depleted Low Permeability Gas Reservoirs
Authors: Fuxa Jason , Di Giampaolo Paolo , Ferrara Giovanni , Di Pietro Mario , Sportelli Marco , Ripa Giuseppe , Di Campli Antonio
Published: April 2019

This paper details a field application of Shaped Memory Polymer (SMP) material for sand management delivering an innovative approach for sand control completions. The use of the technology has enabled profitable exploitation of residual reserves in a mature gas field offshore Adriatic Sea. The paper reviews details of the field deployment, with both economic and well performance results described.

The offshore field was discovered in 1971 and 102 wells have been drilled to date. The trap is a very gentle, slightly asymmetrical anticline made by Pleistocene sandy turbidites, sedimented on the underlying carbonate substrate. Methane gas bearing layers have been sealed by several argillaceous intercalations that worked also as the source rocks of this multilayer reservoir. The sandy layers in this Pleistocene sequence, have thickness ranging from few centimeters up to some meters, and porosity from 22 up to 33%. Isolation of multiple gas-water contacts and fines production have been two crucial issues while producing the field.

Since 2000, all seven platforms in this field have required workovers by means of performing sidetracks. Due to the reservoir characteristics, the well interventions have been completed with multi-layer, stacked cased-hole sand control completions. Despite a continuous improvement of procedures and technique, the traditional sand control methods have been efficient but were no longer profitable, due to challenging market conditions.

An open-hole completion using SMP combined with zonal isolation and selective production has proved to be an effective alternative to cased-hole sand control. This novel completion approach resulted in a significant reduction in both cost and rig time. It is estimated that nearly two weeks of rig time was saved and an overall workover cost reduction of approximately 35%, with further efficiencies to be realized on upcoming deployments. To date, the completion has proved to be an effective sand control method, with no produced solids, no plugging effect, and gas production that has met expectations.
A Comparison of Gas Hydrate Petroleum Systems in Marine and Permafrost Regions
Authors: Lau Hon Chung , Zhang Ming , Wang Jinjie , Huai Yinchao
Published: April 2019

In this paper, we present for the first time, a classification system for naturally-occurring gas hydrate deposits existing in the permafrost and marine environment. This classification is relatively simple but highlights the salient features of a gas hydrate deposit which are important for their exploration and production such as location, porosity system, gas origin and migration path. We then show how this classification can be used to describe eight well-studied gas hydrate deposits in permafrost and marine environment. Potential implications of this classification are also discussed.
The Application of CBM Case Library Based on Data Mining
Authors: Qiu Maoxin , Zhang Huazhen , Zhang Huanzhi , Liu Jia , He Yanqing , Wang Lu , Zhang Jiaming
Published: April 2019

The development of China's coalbed methane (CBM) industry is restricted by the complex geological conditions, unmatched technology and lack of development experience. To solve this problem, a case library covering typical CBM fields at home and abroad is established. Through data analysis and mining, the differences between domestic and foreign CBM fields are compared and the influence factors of CBM single well production were analyzed.

This study includes the data preparation of CBM fields, the establishment of the case library system, the establishment of data analysis model and the result analysis. The data of case library covers the geological conditions, development history, main technology and economy of CBM field. The case library is based on the MVC development idea and adopts the object-oriented method. The analysis of data includes correlation analysis of single well production and quantitative gap analysis.

The case library contains a number of typical case data, such as San Juan, Black warrior, Bowen, Surat, Qinshui, Hancheng, etc. The relevant parameters of different CBM fields can be quickly compared by using the case library. By mining the data such as coal rank, permeability, thickness, depth, gas content and proved reserves, the influence factors of single well production of CBM well are analyzed quantitatively. It is found that the thickness and permeability of coal seam have the greatest influence on single well production. Quantitative gap analysis shows that there is a large gap between the coal seam thickness, permeability, the gas drainage technology and well production improvement technology of domestic CBM fields compared with the foreign fields with the best development effect.

Through the application of CBM case library, data is analyzed and utilized effectively and data values are fully exploited. This study provides an effective way to analyze the gap of CBM in China and draw lessons from abroad.