bluuebunny/crossref_metadata_2025_split huggingface dataset:
Application of Temporary-Blocking Fracturing Technology in Casing-Deformed Shale Gas Well
Authors: Naizhen Liu , Ming Liu 
Published: October 2018

Abstract
In the past five years, as one of the most active country for the shale gas development all over the world, China has been experiencing a boom of shale gas development. In 2017, the total yearly production of shale gas has reached about 350 BCF in China. As the planning goes on, the yearly production will reach 1000 BCF in 2020. The market is huge regardless that the task is difficult.
There are four national shale gas demonstration plots in China, CW plot, JSB plot, ZT plot and YA plot. JSB plot is the first to obtain breakthrough for the shale gas development, contributing the half of the total yearly production of shale gas in China. CW plot is the second successful plot, which contributes about 30%. This paper will describe the casing deformation which is the knottiest problem not only CW plot but for all plots.
The casing deformation of shale gas wells in China happens frequently, which restricts the gas production to a great extent. This paper describes the application of temporary-blocking fracturing technology in a casing-deformed shale gas well to minimize the loss. In this well, only one stage of hydraulic fracturing is conducted leaving 19 stages (about 1400m) untreated due to the casing deformation. First of all, the wiper trips are made to confirm the deformation point is around the drilling target spot A, and the maximum drift diameter decreases from 114mm to 83mm. Since there is no smaller bridge plug, then the temporary-blocking fracturing techonology is determined to be conducted. 16 stages are designed for the 1400m interval. For feasibility, the 16 stages are separated into 8 rounds of fracturing. A total of 7756 blocking balls and 2750kg blocking agent are used to block the perforations for the 16 stages. To enlarge the stimulated reservoir volume (SRV), the volume of fracturing fluid and the quality of proppant injected for one stage are designed as 53Mcf and 120t respectively. The treatment pressure indicates that the pumped blocking agent is effective. From putting the well on production, the average daily production is 3.53MMcfd which is no less than that of wells without casing deformation in the same pad. Based on the chemical analysis of the collected flowback fluids, the blocking agent is 100% dissolved and has no damage to the formation. The application of this technology successfully solves the problem of casing deformation so as to reduce the production and economic loss.
A Precise MPD Technology to Reduce Risk in Drilling of Fractured Cavernous Carbonate with Narrow Pressure Margins
Authors: Chen Peng , Zhou Yingcao , Liu Wei , Wang Junjie 
Published: October 2018

Abstract
It is effective to drill horizontal wells in carbonate to increase production. However, the horizontal sections were limited and hard to be extended by means of conventional drilling due to high risk of drilling in fractured cavernous carbonate. Application of a precisely pressure controlled drilling system was developed to have successfully drilled and extended horizontal sections, reduced risk of drilling in the said kind of wells with narrow pressure margins in western China’s Tarim basin.
A comprehensive MPD technology with 9-operational situations, 4-controlling modes and 13-precise controlling techniques of emergent changeovers was built up through full-size laboratory test, field test and deployment. Under-, near-, or over-balanced MPD was selected and carried out to meet diversified requirements based on proper well trajectory design, build-up rate control, retention of margin for adjustment and control of the well track, dynamic prediction of bottomhole pressure alternation while drilling according to the stability of the formation and whether toxic gases existed.
Drilling in Tarim basin usually experienced complex geology, narrow density margin, low ROP, frequent downhole complex and accidents, and long drilling duration. After the precise MPD technology being applied in Tarim basin, the risk of kick-and-loss coexistence has been reduced and the well cost has been gained beneficial results. The application assisted not only the hydrocarbon discovery of reef flat geology of Ordovician system in China’s Tarim basin, but also the well deliverability enhancement, effective treatment of downhole complex, and improvement of ROP. Application of precise MPD in a Tarim horizontal well created a record for deepest horizontal well with MD at 8,008m, TVD at 6,327m, and horizontal section of 1,551m. Another Tarim horizontal well produced a new record of daily footage 150m and horizontal footage 1,561m, and 42 pay zones were discovered. The difficulty of horizontal section pressure control in fractured cavernous carbonate was effectively resolved and multi combinations of fractures and caves were drilled through by application of precise MPD technology. The horizontal sections, historically limited by 200m-300m, were largely extended in fractured cavernous carbonate horizontal wells, and the well capacities were advanced.
Drilling of fractured cavernous carbonate horizontal wells is an integration and innovation of the precise MPD technology, downhole risk control, and the optimization and control of horizontal well trajectory. The precise MPD technology could effectively avoid or alleviate downhole risk, cut non-productive time, extend horizontal section, promote rate of penetration, reduce drilling cycle, achieve safe drilling, and therefore reduce well cost. It would play a significant role in future challengeable drilling activities.
Geosteering in a Complex Deepwater Reservoir in the Niger Delta
Authors: Ndokwu C. , Foekema N. , Okowi V. , Olagundoye O. , Umoren N. , Delpeint A. , Ndefo O. , Agbejule A. , Jeje O. 
Published: October 2018

Abstract
Geological and geophysical uncertainties account for most of the challenges encountered during the placement or geosteering of high-angle and horizontal wells in deepwater environments. Structural uncertainties could result from the targeted subsurface structure that is folded, undulating and faulted. Lateral discontinuity of sand bodies, lateral variations in sand thickness, multiple beds, and formation heterogeneities are some of the more common sedimentological uncertainties. Geophysical uncertainties include the vertical depth of the seismic data and seismic reservoir characterization. These uncertainties make increasing the likelihood of success during geosteering not only dependent on the integration of geologic and seismic reservoir characterization techniques, but also on the application of a robust reservoir navigation scheme.
In this paper, we present a case study of the geosteering of a horizontal producer well in a complex reservoir in the deep offshore Niger Delta. The reservoir consists of highly faulted channelized turbidites. The lateral discontinuity of sand bodies and the variations in sand thickness have been calibrated by other producer wells in the field. For efficient geosteering, geological and geophysical well planning was complemented by the availability of scenario modeling, a suitable drilling strategy, the availability of fit-for-purpose drilling and formation evaluation tools, robust software, and a multidisciplinary team with the right mix of experience for effective reservoir navigation. An extra-deep reading azimuthal propagation tool was used, and the inversion was performed with Multi-Component While Drilling (MCWD) software that utilized an algorithm to perform real-time processing of any combination of the deep and extra-deep logging-while-drilling (LWD) resistivity measurements, both coaxial and azimuthal [Sviridov et al., 2014].
The case study primarily reviews the geological and geophysical strategies employed during the geosteering, examines the role the extra-deep azimuthal resistivity inversion modeling and borehole imaging played in understanding the nature of the reservoir and checking the effect of formation anisotropy on depth of detection. The study highlights some peculiarities of the depositional environment of the area and shows the benefits of having extra-deep azimuthal propagation resistivity tools in the bottom hole assembly.
Successful Snubbing Application Performed Underbalanced Fishing of Parted Coiled Tubing in Live High-Pressure Well: Offshore Vietnam
Authors: Wattanasuwankorn Reawat , Daohmareeyor Tuanangkoon , Kritsanaphak Kritsana , Pathmanathan Indran , Bohorquez Jorge 
Published: October 2018

Abstract
Approximately 3,762 m of coiled tubing (CT) became stuck downhole in a live, offshore high-pressure well. The CT parted after fatigue limitations were exceeded.
This paper discusses a snubbing operation that was conducted to fish the parted CT. To ensure flawless execution the following was employed:
Successful job design, operational planning, and execution. A complex engineered solution to improve the fishing operation and clean up debris. Introduction of well control applications (hot tapping) to help minimize risk of pressure becoming trapped in the CT. Multiple successful trials.
A unique job design was introduced and executed according to plan. Careful engineering, study, and yard trials supported the actual operation. The crew's technical expertise helped improve safety and enhanced efficiency.
Significant underbalance skill and fishing proficiency helped make the fishing operation successful. The operator and service company improved their understanding and operational competence by fully communicating with all parties involved.
The operator was able to remove parted CT and perform plug and abandonment (P&A) operations in this live, high-pressure offshore well with no incidents or spills. The successful engineering and testing during this campaign are discussed.
Carbonate Acidizing and Flowback Analysis- A Review and an Evaluation Method
Authors: Aldakkan Bashayer , Al Moajil Abdullah M. , Alnoaimi Khalid 
Published: October 2018

Abstract
Acidizing treatments are the primary technique to enhance production of carbonate formations. Analysis of historical matrix treatment flowback, and laboratory assessment provide insights on the reservoir response to the acid recipe, and thus, positively enhance the selection of fluid recipes. The objective of this paper is to share an evaluation method to assess the effectiveness of an HCl-based acid recipe through experimental studies and flowback analysis.
Gelled, emulsified, and straight hydrochloric acids (HCl) were used to demonstrate the method. Inductively-Coupled Plasma (ICP) was utilized to characterize the liquid flowback samples. HP/HT filter press test was conducted using oil-based and water-based drilling fluids at 150°F to examine the integrity of filter cake and the removal means. Compatibility between crude oil sample and the acid recipe was conducted under reservoir conditions using HP/HT aging cell. ICP analysis was used to correlate the calcium concentration to the magnitude of the rock dissolved by the selected acid recipe.
Filter cake removal using water-based and oil-based drilling fluids showed an effectiveness of 90% and 94.8%, respectively. Clear separation was observed between the oil sample and the acid recipe for the slightly gelled and fresh acid formulas. Calcium and magnesium concentration profile in flowback samples indicated the time when spent acid was recovered. Reduction in calcium concentration suggested calcium-based precipitation occurrence. The pH profile, in combination with density measurements, can assess the optimum shut-in and flowback time for full acid spending and retrieval. Steady pH profile at later times of the flowback revealed the presence of carbonic acid. The iron profile analysis was critical to determine the presence of corrosion products and the origin of iron ions in combination with chromium and manganese ions. Dilution factor of sodium and potassium ion concentration was used to determine water cut in acid flowback samples.
Fracture Optimization Orientated Geosteering within a Fracable Window can Improve Production Performance
Authors: Yao Yanhua , Ning Zhang , Li Qirong , Yang Yang , Jian Zheng , Man Chen , Li Yang , Hao Zhou , Zhou Zhang 
Published: October 2018

Abstract
Production in shale is highly related to the well placement in both sweetspot and fracable zone. Due to both, market conditions and also shale property, geosteering in tight shale reservoirs have generally employed basic and economical steering tools, such as gamma ray; however, though the tool provides some data to steer the well, the data provided does not allow for predictions of fracability and production potential of the shale rock. This paper introduces a new geosteering approach, which augments existing techniques by providing data to also help well placement, then design stage and perforation location. This novel formation evaluation technique is essentially building a quantitative model of "sweetspot fracable window" for shale, which can help to land and target most prospective zones. The main quantitative data is obtained through measurement of cuttings samples at well-site in semi-realtime on a field portable SEM (Ashton et. al., 2013), generating the mineralogical and elemental composition of the samples, and also providing rock textural data. Although cuttings are evaluated after the well being drilled, cuttings are only physical representative rock samples from the bottom of the hole.
Case studies presented in the paper have shown that maintaining the well path in the sweetspot fracable window can result in better well production after fracturing. Thus, the goal for geosteering is to ensure as much as possible that the horizontal well trajectory is maintained within this window. Additionally, the cuttings data generated during the drilling process can also be used both during and after TD to generate optimized completion design, aiming to further maximize well productivity. The cases’ study in this paper also shows that, compared with conventional wireline logging data, the on-location cutting based analysis is able to generate richer mineralogical and elemental data throughout lateral wells, providing a better understanding of geological heterogeneity. Meanwhile, the authors also apply several strategies to calibrate the cutting depths and cuttings’ time lags.
The authors created an approach, which can provide a fast analysis for enhanced reservoir navigation, to keep the well trajectory within a predefined sweetspot fracable zone. The production analysis of the wells, hereafter, verifies that the higher the rate of intersecting into sweetspot fracable zone, the higher production the well receives. This approach then assists in generating cost-effective completion optimization of stage placement and perforation, with the ultimate goal of increasing the investment returns.
In conclusion, the production statistics of the wells verifies the higher rate of intersecting into sweetspot fracable zone, the higher production the well receives. The goal for geosteering is to ensure as much as possible that the horizontal well trajectory is maintained within this window.
The Platform to Optimise the Stranded Well Potential
Authors: Bakar Hasmizah , Watchawong Dangchin , Sahar Raja Nor , Saleh Malaz , Muhaimin Wan Firda , Jeffrey Suzanna Juyanty , Yahia Zaidil 
Published: October 2018

Abstract
During the low oil price period, PETRONAS Carigali Sdn Bhd (PCSB) embarked on an intensified approach to prioritize the production enhancement and idle well reactivation (PE/IWR) activities in its Malaysia operations. To monetize the remaining reserves from these 2,000 active and idle strings, comprehensive opportunity management system which covers opportunity identification, evaluation and prioritization, planning, execution and tracking the activities are implemented.
The identified opportunities from the active and idle wells inventory and integrated field review are initially assessed at a high level based on three criteria, value (the estimated Unit Enhancement Cost, UEC), probability of success and doability which indicates how quickly it will be restored. After the due diligence work completed, the opportunities will progress to the multi-disciplinary technical commercial value assurance committee for approval then followed by planning and scoping the detailed execution. All prioritized, approved and planned opportunities are then turned into execution pipeline and properly tracked into a systematic methodology for post job analysis, evaluating the success of the jobs and recording the lessons learnt for improved future jobs is also addressed in this article.
This article also outlines the examples of comprehensive and successful approach of idle string reactivation activities which gone through this opportunity management system via fishing operation, scale removal treatment, gas lift optimization, behind casing opportunities, acid matrix stimulation and surface facilities rejuvenation. This approach has significantly improved the percentage of active wells in entire domestic operation from 50 to 53%.
Circulating Temperatures in Complex Wellbores: A Quasi-Exact Solution
Authors: Chandrasekhar Sharat V , Suryanarayana P. V. , Sathuvalli Udaya B. 
Published: October 2018

Abstract
Exact solutions are presented for the circulating temperature profiles in an arbitrarily complex deepwater HP/HT well. The methodology is based on coupling multiple segments via interface temperature matching conditions, and can handle deviated wells curvature, tortuosity, variable lithology and multiple geothermal gradients. Frictional heating both at the drillbit and due to the Negative Joule-Thomson Effect are included by coupling the flow hydraulics to heat transfer. These have been largely neglected in previous studies Both forward and reverse circulation scenarios are considered, as are temperature changes across the drill bit at the hole TD. Heat transfer to the ambient and atmosphere above the mudline through the riser are also included in the formulation. Variable fluid thermophysical properties are accommodated by an iterative application of the derived exact solutions. Non-Newtonian flow effects based on the rheological parameters of the fluid are considered in both the hydraulics and heat transfer aspects of the circulating flow.
The method is numerically stable, robust and capable of handling virtually all scenarios in conventional overbalanced drilling. Despite the complexity of the underlying problem, the solution can be implemented in a programmable spreadsheet.
The results show that the circulation rate and inlet temperature have the greatest influence on the circulating temperatures while ROP has a minimal impact because of the pseudo-steady state heat transfer conditions. The key finding is that ignoring frictional effects can result in substantial under-prediction of circulating bottomhole temperatures at higher flow rates, particularly for synthetic/oil-based drilling fluids.
Enhancing Technology Development Process Through Purpose-Built Testing and Training Facilities
Authors: Johnson Austin , Fraczek Justin , Anderson Bo 
Published: October 2018

Abstract

Objectives and Scope
A full-scale test facility is integral during design verification testing of an active Managed Pressure Drilling (MPD) wellbore sealing system as a means to rapidly deploy the technology. The Active Wellbore Sealing System uses a novel sealing element design. Through iterative Finite Element Analysis (FEA) modeling, elastomer composition changes, and immediate feedback from full-scale testing, the first-generation sealing element design performed as intended during its first deepwater field trial in live drilling operations. Further, as the testing took place, the crew was able to prepare and practice planned procedures in a safe environment prior to going offshore.
The test rig facility was upgraded for testing operations with the second-generation Active Wellbore Sealing System. The use of drilling mud combined with simultaneous stripping and rotation of drillpipe under realistic wellbore temperature and pressure enables ‘drilling mode’ testing which exceeds API 16RCD requirements. Use of production equipment at the test rig facilitates automation development to enhance wellbore seal life. Further, trained crews operate the MPD field equipment at the facility and can practice planned drilling procedures. By mirroring the conditions observed in the field, the test rig facility is instrumental in the delivery of project-ready MPD technologies.

Methods, Procedures, Processes
This paper will share test data from the design verification testing program to demonstrate how use of the full-scale test center results in a project-ready system by simulating actual drilling conditions. Additional design verification testing of the second-generation Active Wellbore Sealing System is ongoing at the time of publication of this paper.

Results, Observations, Conclusions
This paper shares results from the design verification testing. The program resulted in successful performance of the sealing element on its first trial. The continued execution of the program reduces the Non-Productive Time (NPT) and cost compared to conventional pilot projects through offline validation, systems integration testing, and ensuring personnel possess the required competencies to efficiently operate the equipment in the field.

Novel and Additive Information
Use of realistic wellbore temperature and pressure with simultaneous stripping and rotating to perform design verification testing was an essential part of the successful first test of the active wellbore seal. Test rig upgrades enable the use of drilling fluid and production equipment to test the second-generation Active Wellbore Sealing System.