Well RXY is located in Cairn’s Ravva offshore field in the Krishna-Godavari Basin in India. One goal for the field was significant crude production by means of a secondary reservoir section. This paper compares the results of gas identification and lithology identification using pulsed-neutron spectroscopy in openhole and casedhole environments. Acquiring data from an abandoned subsea well has been done before, but never quite like this. As I read through the abstracts and papers that have been presented in the past year, I notice several key themes: verification of cement placement, development of new materials as a barrier, development of new additives to improve the cement barrier, and enhancement of existing techniques.
Your submission must be received by 12 June 2019. The February 2019 issue of JPT® magazine had several articles related to formation damage. Peruse them below to gather inspiration before you submit. Novel fluids, tools, and techniques Injectors vs. producers Selective/oriented perforating Acidizing and acid fracturing (acid sludge prevention and acid flowback analysis) Acid diversion Hydraulic fracturing and frac packing (frac fluids, proppants, fluid loss additives, closure stress, embedment, tortuosity, perforations, and relative frac/wellbore orientation) in vertical, high-angle and/or horizontal wells Shale fracturing (slick water, crosslinked polymer, hybrid) Optimizing results of perforations-underbalanced, extreme overbalanced, and remedial cleanup Fluid flowback Proppant flowback Fracture mapping (fracture height and half length) Acoustic damage removal (may fit under novel fluids, tools and techniques)
Devshali, Sagun (Oil and Natural Gas Corporation Ltd.) | Manchalwar, Vinod (Oil and Natural Gas Corporation Ltd.) | Deuri, Budhin (Oil and Natural Gas Corporation Ltd.) | Malhotra, Sanjay Kumar (Oil and Natural Gas Corporation Ltd.) | Prasad, Bulusu V.R.V. (Oil and Natural Gas Corporation Ltd.) | Yadav, Mahendra (Oil and Natural Gas Corporation Ltd.) | Kumar, Avinav (Oil and Natural Gas Corporation Ltd.) | Uniyal, Rishabh (Oil and Natural Gas Corporation Ltd.)
The paper describes the feasibility of revisiting old sands, for improving the recovery factors and enhancing production, which otherwise were already abandoned. The paper also outlines the systematic methods for predicting the onset of liquid loading in gas wells, evaluation of completions for optimization and comparison of various deliquification techniques. ONGC is operating in two gas fields in eastern and western regions in India. Earlier in both the fields, many sands had to be closed/isolated after the wells ceased to flow due to liquid loading in the absence of continuous deliquification. In order to predict liquid loading tendencies and identify opportunities for production enhancement, performance of 150 gas wells has been analyzed. To select most suitable deliquification technique for the present condition, all technically feasible methods have been evaluated and compared in order to get the maximum ultimate gas recovery possible.
After an extensive study, 3 wells were identified in the preliminary stage and SRP was selected as the most suitable Deliquification technique. Initially, two non-flowing wells, which had ceased due to liquid loading and were about to be abandoned, were selected. After SRP installation and sustained unloading of water for about 30 days, these wells started producing 12000 SCMD gas. In the third well, one of the top sands had earlier been isolated due to liquid loading and production history indicated that the isolated sand had a very good potential. Also, production from the well was declining in the current bottom operating sand as well due to liquid loading. Encouraged by the results that deliquification had yielded in the initial two gas wells, the isolated sand interval in the third well was opened again with the aim to revive production. The well was re-completed with SRP with both the reservoirs open. Before deliquification, the well was producing about 15000 SCMD gas from the bottom sand. After SRP installation and continuous deliquification, the well started producing gas at a stabilized rate of 45000 SCMD, thereby resulting in an additional gas recovery of 30000 SCMD for nearly one year as on date. The approach of putting in place continuous deliquification techniques has not only helped in enhancing production from the existing reservoirs, but has also opened up new avenues to revisit the earlier isolated / abandoned reservoirs for possible enhanced recoveries.
Case studies of mill-out operations in the Permian Basin which evaluate chemical programs and processes used. Results show how existing processes and chemicals used or lack thereof, can affect equipment and undo the preventative chemical treatments used during the hydraulic fracturing process.
The study looks at field water testing performed during various mill-out operations and considered workover rig vs coiled tubing, equipment set up, water & chemicals used, and operational challenges. Water analyses were completed on the injection water and returns at various intervals of the mill-out. Effectiveness of chemical treatment was also monitored when biocide was used.
Field case studies of horizontal wells for two operators in the Permian Basin are presented. Wells were milled-out utilizing workover rigs or coiled tubing units. Testing results show the impact of equipment setup and operations process on the water quality and efficiency of the chemicals used. Water fouling was prevalent in all cases, with coiled tubing jobs showing the highest degree of water contamination and chemical inefficiency. Changes in the water treatment program during operations showed significant improvement and sustainable results. Potential corrosion of the work string due to water fouling and water composition were also observed. The effects of changes to chemical dosages were also monitored. This was important because it identified operational improvements that can reduce equipment replacement costs, reduce chemical overuse and help protect wells from fouling due to high bacteria.
These case study provides a comprehensive review of mill-out operations, which provides guidelines for improving chemical efficiency and potential of extending life of the work string.
Wu, Zengzhi (CNPC Chuanqing Drilling Engineering Co. Ltd., Drilling & Production Engineering Technology Research Institute) | Zou, Hongjiang (CNPC Chuanqing Drilling Engineering Co. Ltd., Drilling & Production Engineering Technology Research Institute) | Wang, Yugong (CNPC Chuanqing Drilling Engineering Co. Ltd., Drilling & Production Engineering Technology Research Institute) | Wu, Long (CNPC Chuanqing Drilling Engineering Co. Ltd., Drilling & Production Engineering Technology Research Institute) | Li, Yong (CNPC Chuanqing Drilling Engineering Co. Ltd., Drilling & Production Engineering Technology Research Institute) | Xu, Yang (CNPC Chuanqing Drilling Engineering Co. Ltd., Drilling & Production Engineering Technology Research Institute) | Wang, Renfeng (CNPC Chuanqing Drilling Engineering Co. Ltd., Drilling & Production Engineering Technology Research Institute) | Meng, QingCong (CNPC Chuanqing Drilling Engineering Co. Ltd., Drilling & Production Engineering Technology Research Institute) | Jiang, Wenxue (CNPC Chuanqing Drilling Engineering Co. Ltd., Drilling & Production Engineering Technology Research Institute) | Wang, Suoliang (CNPC Chuanqing Drilling Engineering Co. Ltd., Drilling & Production Engineering Technology Research Institute) | Li, Shan (CNPC Chuanqing Drilling Engineering Co. Ltd., Drilling & Production Engineering Technology Research Institute) | Li, Dan (CNPC Chuanqing Drilling Engineering Co. Ltd., Drilling & Production Engineering Technology Research Institute)
With the development of Chang Qing Oilfield, the following technical problems are faced: the increasing proportion of the low-production and low-efficiency wells, the worse production of pertinence and effectiveness in conventional retreatments and a large amount of remaining oil between wells and layers. In this case, the technique of radial fracture network fracturing and deep plugging has been proposed. Meanwhile, the matching products which include variable viscosity diverting acid, micro expansion high strength plugging agent and temporary plugging agent (oil soluble, water soluble and anti-scale) have been developed as well. Nowadays, the retreatment technology has been successfully tested and popularized in Chang Qing oilfield. Compared with the conventional retreatments, these two technologies have remarkable effect on increasing production and prospective application.
Xi, Shengli (PetroChina Changqing Oilfield Company) | Hou, Yuting (PetroChina Changqing Oilfield Company) | Li, Xianwen (PetroChina Changqing Oilfield Company) | Hu, Xifeng (PetroChina Changqing Oilfield Company) | Liu, Peng (Schlumberger) | Zhao, Xianran (Schlumberger)
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.
In hydraulic fracture stimulation of conventional reservoirs (e.g. tight gas and deepwater unconsolidated sands), the use of sophisticated design models is almost indispensable. Typically, each hydraulic fracture is sequentially pumped and executed from near vertical wellbores. It is well understood that the optimum post-fracture well productivity is directly linked to hydraulic fracture dimensionless conductivity, which is governed largely by propped fracture length and width. From an engineering and operation execution point-of-view, the goal is to pump into the fracture and pack it with the desired volume of proppant without encountering premature ‘screen-out’. Therefore, the prediction of fracture geometry, the selection of ‘pad’ volume and proppant pumping schedule become critical for propped fracture design. In practice, a wide range of models have been deployed successfully. However, such considerations do not appear to be important for unconventional resources where multiple fractures are pumped from a long horizontal well. In fact, multi-frac horizontal well technology has advanced through field trials and experimentation, often without much help from modeling or understanding of multiple-fracture mechanics. This begs the questions of what areas of research and model design parameters should we focus on? Can we avoid the details while dealing with the big picture such as fracture spacing, horizontal well length/direction, the well's landing depth, and their impact on cost and production?
This extended abstract revisits the motivation and well-accepted design approach for hydraulic fracturing in conventional reservoirs and some of the challenges facing hydraulic fracturing design in unconventional reservoirs. Practical first-pass design considerations based on geomechanics for fracture spacing and horizontal well landing depth selection are outlined.
Liu, Hongtao (PetroChina Tarim Oilfield Company) | Cao, Lihu (PetroChina Tarim Oilfield Company) | Xie, Junfeng (PetroChina Tarim Oilfield Company) | Yang, Xiangtong (CNPC Engineering Technology R&D Company Limited) | Zeng, Nu (PetroChina Tarim Oilfield Company) | Zhang, Xuesong (PetroChina Tarim Oilfield Company) | Chen, Fei (PetroChina Tarim Oilfield Company)
There is abundant natural gas in Kuqa foreland area of Tarim basin, the reservoir has characteristics of ultra depth(6500m-8000m), high pressure(115MPa-140MPa), high temperature(170°C-190°C) and complex corrosive medium, which bring well integrity high challenge. There are 52 production wells in the Kuqa foreland basin in 2012. The 16 wells of these production wells exist sustained casing pressure(SCP). The SCP wells caused by the tubing string failure is 61%.
Since 2012, in order to build safe well barrier and achieve scientific production management, consider all important periods of drilling, well testing, well completion and production in well full life cycle. the design methods of the four main well barrier components(casing string, cement, tubing string, well head) are optimized. A set of technology for well barrier quality control, well maintenance and well production management is formed. Finally, the key technology of full life cycle well integrity for ultra depth, HPHT gas well is formed.
In view of the large angle of bedding, well deviation controlled difficultly, and coexistence of high pressure saline aquifer and week bed in one open hole section which lead to serious casing wear and poor cement stone, the vertical well drilling technology, the collapse resistance casing design methods, the casing wear preventing measures, negative pressure test method and high temperature, high density cementing technology are completed. These technologies improve the safety of casing string and the quality of cement. Considering the extreme working conditions(the partial pressure of CO2 is beyond 2MPa, The content of chlorine is about 80000mg/L, acid job, 136MPa pump pressure in well head)of tubing string, material selection method, triaxial stress analysis method, quality control technology for tubing string is optimized. The failure ratio of tubing string reduced from 50% in 2013 to zero in 2017. Referencing API RP 90-2 and IOS16530-2, a special calculation method for annulus pressure management is formed, which include minimum operation pressure and maximum allowable pressure for different annulus. Then a risk assessment system is established. The SCP wells is controlled less than 22% in the condition of increasing number of high pressure gas wells.
Based on the research introduced above, China's first set of well integrity specification series is completed. The integrity specification series include the well integrity guide, the well integrity design and the well integrity management for high temperature high pressure and high sulfur gas. These results effectively support safty in production for high pressure gas field in Tarim basin, and will promote the well integrity level in the same kind of oilfield.