In late 2010, Shell began an Eagle Ford appraisal program at Piloncillo Ranch in South Texas. These wells are 8,500’ – 9,500’ TVD horizontals, with an average total depth of 14,500’ MD. Their primary target is the Cretaceous Eagle Ford shale. The Shell leases are located in the gas-condensate window. Shell is currently running a five rig development program. Initially, reservoir pressures were thought to be in the 12.5 ppg range, but Diagnostic Fracture Injection Tests (DFITs) showed the actual pore pressure to be greater than or equal to 14 ppg. Initially, underbalanced drilling techniques were used to drill the 14-14.5 ppg formation with 11 ppg oil based mud. The Eagle Ford has no natural fractures in this area. As more wells were drilled, however, completion fracturing of offset wells began to cause well control problems, as induced fractures were encountered in horizontal sections during drilling. Initially, it was thought that additional casing strings would be required to deal with the higher pressures and flow capability of the 14-14.5 ppg fracture; however, through well control modeling and experience with underbalanced drilling in other tight gas environments, tripping and heavy pill spotting procedures were developed that allowed the wells to be drilled with the initial casing program. This paper will describe the development of fit for purpose well control techniques used to drill underbalanced horizontal wells in the Eagle Ford shale gas play. It will discuss how the characteristics of tight shale formations in horizontal wells resulted in a different approach to well control and tripping procedures. Several simple techniques for establishing an understanding of real time data have helped to make decisions in the field with current information: Institute a dual density system to stop reservoir flow and prevent up-hole lossesCreate a Horner Plot for distinguishing ballooning from reservoir flow if losses are experiencedCreate a mud weight vs. influx flow plot for predicting flow changes with mud weightAscertain how the influx rate and location affect the time at which it would a take a well to unload to dry gas The paper will also describe the software modeling used to determine influx responses and the methodology developed around it. This methodology is applicable to other tight shale formations drilled horizontally and developed around the globe. These procedures can significantly reduce non-productive time and minimize serious well control events on horizontal shale wells when properly followed.
Summary An analysis of 72 workover tubing cuts made were completed to determine the effect of well variables on the cutting performance of chemical, jet, and radial cutting torch (RCT) tubing cutters. Performance data indicated that cutting success was only 65, 50, and 77% for the chemical, jet, and RCT cutters, respectively. While it was found that some cutting failures could be attributed to specific causes, such as heavy paraffin in the well, improper detonation, low-pressure tool leaks, exceeding tool pressure limits, and improper tool gas ventilation, other failures did not have any apparent cause. Therefore, the data was analyzed against specific well variables to look for trends to determine other possible failure causes. The most significant results indicated that chemical cutter success in CaBr2 completions fluids was significantly reduced. For comparison, cuts in bromide fluids accounted for 71% of the total number of failed cuts but only comprised 32% of the total attempted cuts. Based on this data, along with examining the chemical reaction between the acid in the chemical cutter, bromine trifluoride, and the other completion fluids, it is believed that the chemical cutter acid reacts more efficiently with bromide completion fluids, therefore, limiting the amount of acid available to sever the pipe. Additionally, it was concluded that placing the pipe in tension significantly increased cutting performance. No other significant correlations were found to other well variables. Introduction Choosing the best cutter for any particular drilling or workover cutting job is not always trivial. Success rates over 72 tubing cut attempts during offshore workovers were only 65, 50, and 77% for the chemical, jet, and RCT cutters, respectively (Fig. 1). Several potential causes likely contributed to this larger than expected number of failures. First, the many logistical and operational issues that must be considered, such as transportation safety, temperature limitations, cut flaring, and wellbore restrictions, often predetermines which cutter must be run, even though it may not be the most efficient choice. Additionally, service companies generally rate tools only based on pipe size, pressure, temperature, and the maximum and minimum standoff between the tool and the pipe wall, even though other well variables are likely important. This is supported by the lower than expected success rates. As well, access to specific cutter performance data is proprietary or limited, and for this reason, it is often necessary to rely on the service company's experience to choose the most effective tool for conditions. This choice is complicated by the fact that service companies tend to specialize on one type of cutter, potentially limiting the possibility that the most efficient cutter for well conditions is selected for the job. This paper has two primary goals:to identify other variables that may be important to cutter performance, andto provide a resource of data that may be useful for tool selection.
fax 01-972-952-9435. AbstractAn analysis of 72 tubing cuts made during Shell deepwater workovers in the Gulf of Mexico was completed to determine the effect of well variables on the cutting performance of chemical, jet, and radial cutting torch cutters.An initial pre-study analysis indicated that cutting success was only 65%, 50%, and 77% for the chemical, jet, and radial cutting torch cutters, respectively. It was found that some cutting failures could be attributed to specific causes, such as heavy paraffin in the well, improper detonation, low-pressure tool leaks, exceeding tool pressure limits, and improper tool gas ventilation; however, other failures did not have any apparent cause. These remaining cuts were analyzed against specific well variables to look for trends that may indicate the cause of failure.It was determined that chemical cutter success in CaBr 2 completions fluids was much lower than all other fluids combined. Specifically, cuts in bromide fluids accounted for 71% of the total number of failed cuts, but only comprised 32% of total attempted cuts. Further investigation indicated that bromide fluids may react more violently with the bromine trifluoride acid than the other types of completion fluids used. From this analysis, it is believed that less acid will be available to sever the pipe wall when cutting in bromide fluids.Additionally, it was found that placing the pipe in tension significantly increased cutting performance.No other significant correlations were found to other well variables.
An analysis of 72 tubing cuts made during Shell deepwater workovers in the Gulf of Mexico was completed to determine the effect of well variables on the cutting performance of chemical, jet, and radial cutting torch cutters. An initial pre-study analysis indicated that cutting success was only 65%, 50%, and 77% for the chemical, jet, and radial cutting torch cutters, respectively. It was found that some cutting failures could be attributed to specific causes, such as heavy paraffin in the well, improper detonation, low-pressure tool leaks, exceeding tool pressure limits, and improper tool gas ventilation; however, other failures did not have any apparent cause. These remaining cuts were analyzed against specific well variables to look for trends that may indicate the cause of failure. It was determined that chemical cutter success in CaBr2 completions fluids was much lower than all other fluids combined. Specifically, cuts in bromide fluids accounted for 71% of the total number of failed cuts, but only comprised 32% of total attempted cuts. Further investigation indicated that bromide fluids may react more violently with the bromine trifluoride acid than the other types of completion fluids used. From this analysis, it is believed that less acid will be available to sever the pipe wall when cutting in bromide fluids. Additionally, it was found that placing the pipe in tension significantly increased cutting performance. No other significant correlations were found to other well variables. Introduction Choosing the best tool for any particular drilling or workover cutting job is not always trivial. A study of 72 tubing cut attempts by one major operator indicated that cutting success was only 65%, 50%, and 77% for the chemical, jet, and radial cutting torch (RCT) cutters, respectively (Figure 1). There are several potential causes contributing to this larger than expected number of failures. First, the vast array of logistical and mechanical parameters that must be considered often makes cutter selection ambiguous. Despite this fact, service companies generally only rate tools based on pipe size, pressure, temperature, and the maximum and minimum standoff between the tool and the pipe wall. Undoubtedly, satisfying the limits of these rated variables is essential for a successful cut; however, the lower than expected success rates indicates there may be other significant factors. It is apparent that many well variable relationships to cutting performance are extremely complex, forcing decisions to often be made from past history or testing. However, access to specific tool performance data is proprietary or limited, and for this reason it is often necessary to rely upon the service company to choose the most effective tool for conditions. This is complicated by the fact that service companies tend to specialize within one particular tool, potentially limiting the possibility that the best tool will be selected for the job. The goals of this paper are two-fold:to identify other variables that may be important to cutter performance, andto provide a resource of data that may be useful for tool selection.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.