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Objective This paper summarizes key engineering discoveries and technical findings observed during the staged development of a volcanic reservoir. Through out the development, 200 hydraulic fracturing diagnostic injection tests and 168 hydraulic fracturing treatments were performed. This program was conducted in one of the few commercially viable thick and laminated volcanic gas reservoirs in the world and were staggered in 5 separate campaigns over an 11-year period. Method, Procedure, Process Due to the low permeability of this gas reservoir, hydraulic fracturing was necessary for sustained economic productivity. As this massive laminated reservoir contained between 15 to 40 vertically separated pay sections, a key design consideration was to connect as much pay as possible with the least number of fracturing stages. Although a conventional plug and perforation frac technique gives full assurance of optimal fractures for every bit of pay, the completion cost would undermine the project's economics. Therefore, the limited entry technique was selected. The uncertainties and risks were evaluated to maximize the probability of success. Both methodologies were applied in successive campaigns. Staggering the project into 5 successive campaigns enabled adequate time to evaluate results, acquire data and execute. The results from these learnings are summarized in this paper. Results, Observations, Conclusions Over 60 DFITs (Diagnostic Fracture Injection Tests), ~90 SRTs and ~50 Mini-Fracs have been conducted. In addition to conventional fracture diagnostics tests, other techniques were applied with successful implementation. One such example was the utilization of multiple step rate tests within the same frac stage to evaluate limited entry efficiency. As a result of the test data, the number of clusters per frac was increased from 3 to 6, increasing the net pay coverage by about 65%. Another achievement was the reduction of the uncertainty in tubing friction and the evaluation of tubing friction increase due to the addition of proppant. This resulted in a cost effective method of reducing uncertainties in calculated BHPs, thus improving the overall understanding of fracture geometry. This paper also demonstrates that the integration of all of the collected diagnostic data, temperature surveys, frac simulation and geo-mechanic calibration resulted in increased contribution from more zones which was verified with production logs. This enhanced reservoir understanding greatly helped to save operational time and reduce cost. Completion improvements have resulted in an 80% increase in productivity and a 20% increase in EUR. Screen out rates have dropped from 33% to 5% between the initial and the most recent campaign. Novel/Additive Information A holistic workflow for conducting diagnostic injection tests in volcanic pays. Detailed analysis of limited entry controlled hydraulic fracturing and its efficiency. Representative case histories including, DFITS, Step rate tests, Mini Fracs, Temperature surveys and production logs to back up the production results.
Objective This paper summarizes key engineering discoveries and technical findings observed during the staged development of a volcanic reservoir. Through out the development, 200 hydraulic fracturing diagnostic injection tests and 168 hydraulic fracturing treatments were performed. This program was conducted in one of the few commercially viable thick and laminated volcanic gas reservoirs in the world and were staggered in 5 separate campaigns over an 11-year period. Method, Procedure, Process Due to the low permeability of this gas reservoir, hydraulic fracturing was necessary for sustained economic productivity. As this massive laminated reservoir contained between 15 to 40 vertically separated pay sections, a key design consideration was to connect as much pay as possible with the least number of fracturing stages. Although a conventional plug and perforation frac technique gives full assurance of optimal fractures for every bit of pay, the completion cost would undermine the project's economics. Therefore, the limited entry technique was selected. The uncertainties and risks were evaluated to maximize the probability of success. Both methodologies were applied in successive campaigns. Staggering the project into 5 successive campaigns enabled adequate time to evaluate results, acquire data and execute. The results from these learnings are summarized in this paper. Results, Observations, Conclusions Over 60 DFITs (Diagnostic Fracture Injection Tests), ~90 SRTs and ~50 Mini-Fracs have been conducted. In addition to conventional fracture diagnostics tests, other techniques were applied with successful implementation. One such example was the utilization of multiple step rate tests within the same frac stage to evaluate limited entry efficiency. As a result of the test data, the number of clusters per frac was increased from 3 to 6, increasing the net pay coverage by about 65%. Another achievement was the reduction of the uncertainty in tubing friction and the evaluation of tubing friction increase due to the addition of proppant. This resulted in a cost effective method of reducing uncertainties in calculated BHPs, thus improving the overall understanding of fracture geometry. This paper also demonstrates that the integration of all of the collected diagnostic data, temperature surveys, frac simulation and geo-mechanic calibration resulted in increased contribution from more zones which was verified with production logs. This enhanced reservoir understanding greatly helped to save operational time and reduce cost. Completion improvements have resulted in an 80% increase in productivity and a 20% increase in EUR. Screen out rates have dropped from 33% to 5% between the initial and the most recent campaign. Novel/Additive Information A holistic workflow for conducting diagnostic injection tests in volcanic pays. Detailed analysis of limited entry controlled hydraulic fracturing and its efficiency. Representative case histories including, DFITS, Step rate tests, Mini Fracs, Temperature surveys and production logs to back up the production results.
Many fields in Argentina have multilayer reservoirs that require various stimulation techniques, primarily hydraulic fracturing. A variety of formations and types of reservoirs, such as conventional (mature fields) and unconventional (tight gas and shale), are the main focus in the Golfo San Jorge and Neuquén basin. The hydraulic fractures created in these basins present a variety of conditions and challenges related to depth, well architecture design, bottomhole temperature (BHT), reservoir pressure, and formation permeability. In 2006, a pinpoint completion technique was introduced to help achieve greater efficiency and reduce time and costs associated with completions. This paper presents experiences gained using this technology and proving such versatility in different types of reservoirs. The pinpoint technique, called hydrajet perforating annular-path treatment placement and proppant plugs for diversion (HPAP-PPD), was applied in new wells at different reservoir conditions. The history and evolution of this technique in Argentina was initiated in conventional oil reservoirs (mature fields in Golfo San Jorge) and then was introduced in the Neuquén basin in gas well completions. Throughout the last seven years, this technique has been tested and implemented in tight gas wells. More recently, it was used to improve a completion technique in a shale oil well. This completion method allowed operators to focus treatments in desired zones using specific treatment designs based on reservoir characteristics. Several case histories are presented for different basins, formations, and reservoirs types, highlighting lessons learned and reduced completion time.
Raageshwari gas field is located in RJ-ON 90/1 Block in western India with Cairn, Oil & Gas vertical of Vedanta limited as the majority partner and Operator of the field. The field is located in a remote environmentally sensitive region which complicates the gas development project. The reservoir comprises streaks of volcanic sands with low permeability (~0.1 mD). Hydraulic fracturing is required to achieve commercial production from the field. Wells are generally drilled to a measured depth of 3500m and are completed with a 3.5" monobore. There have been 5 fracturing campaigns to date in the field. The previous campaigns were plagued by inefficiencies due to operational, technical, and logistical issues which resulted in cost over-runs. This paper describes the key learnings that were attained and implemented during the last campaign in which ~ 100 fracturing treatments were successfully pumped. Learnings and observations from the campaign can be placed into four categories: HSE: Observations made through the campaign which reduced a) the risk in operations, b) waste generation and c) gas flaring (almost no flaring was required in the last campaign).Operational learnings: Including on-site lessons learnt during the fracturing treatments, post-frac coil tubing cleanout, and post-frac surface well testing. Implementation of these learnings enabled significant completion efficiency gains by the end of the campaign.Technical learnings: Key elements of the frac design and treatment which resulted in more effective treatments. The percentage of reservoir connected with fractures increased more than 30% which had significant impact on well productivity and estimated ultimate recovery (EUR).Contractual learnings: Key points that improved contract management and resulted in efficient and smooth running operations. As a result of implementation of the lessons learnt, days per frac and cost per frac were cut in half. The fracturing campaign was completed ahead of schedule without any LTI incident. Implementation of these learnings resulted in exceptional improvements in the HSE performance, operational efficiency, and well performance which has significantly improved the economics of this tight gas development project. These learnings are applicable to any non-conventional tight gas development project and are especially important given the current market conditions which require a focus on efficiency and adaptation.
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