Good perforating design is essential in maximizing the value that can be pulled from the reservoir. Poorly-planned and/or executed perforating strategies in high-pressure, deep-water wells can easily increase operational costs and reduce production and revenue streams. With the increased demand for oil and gas over the last decade, operators have been forced to explore deeper to find the most prolific reservoirs to meet this growing need. In the U.S. Gulf of Mexico, these deep-water opportunities have required constant improvements to equipment and services to increase their technical capabilities for performing in more critical environments while minimizing non-productive time (NPT). Higher shot densities, propellants, larger perforating guns, electronic firing heads, shrouded assemblies, and dynamic shock modeling have been used to meet these new challenges. A major problem with these deep wells is the increased cost it takes to develop them. The use of more powerful perforating systems to increase flow area is required to maximize well productivity and recoup this cost. With the use of such systems comes the additional explosive load and the difficulty in predicting dynamic wellbore behaviors that could cause tubulars to burst, collapse, bend, buckle, and shear, as well as tubing to move excessively, packer seals to fail, and packers to unset as perforating guns are detonated. Understanding and mitigation of dynamic events at gun detonation, in addition to solid loading imparted to the tubulars, packers, and other completion hardware in the perforating assembly, were needed if the industry was to continue exploring new frontiers with complex challenges. A high-confidence level was needed to use these larger gun assemblies to go forward with these well completions without incurring NPT. This paper discusses a successful execution of a high-pressure, deep-water shoot-and-pull job with a custom-designed bottomhole assembly to address casing integrity challenges and the dynamic shock-modeling software program that evaluates the mechanical integrity of all well components.
Oilwell casing perforating has been used in the industry since 1932 and was pioneered by the Lane-Wells Company who introduced the bullet-gun perforating technique. Shortly after the introduction of the bullet gun, explosive jet perforators were introduced, which provided a different and more aggressive way to perforate casing.With the increased demand for oil and gas over the past decades, operators have been forced to explore deeper, hotter reservoirs to find the most prolific reservoirs. These deepwater opportunities have required constant changes to equipment and services to increase their technical capabilities for performing in more critical environments. Perforating with higher-shot densities, propellants, and larger perforating guns has been ongoing to meet these new challenges.A major problem with these increases, however, is the difficulty in predicting dynamic wellbore behaviors that cause tubulars to collapse and bend and packers to unset as perforating guns were detonated. Research to understand the pressure behavior during the perforation event, in addition to the solid loading that is imparted to the tubulars, packers, and other completion hardware in the perforating assembly, was needed to enable the industry to go forward with a high level of confidence that wells could be completed safely and cost effectively.This paper discusses a shock-wave computer modeling program that evaluates the mechanical risk factors of well components to ensure that the health, safety, environment, and service quality needs in a design are addressed. A timemarching, finite-differences technique is applied as the numerical method for both fluids and solids. The software is installed on a personal computer and typically executes the models within several minutes to several hours, depending on the complexity of the job design.The physics-based model has been validated (Schatz et al. 1999;Schatz et al. 2004) with special high-speed recorders that sense pressure, temperature, and acceleration at a sampling frequency of 115,000 samples per second.This paper provides data from offshore oil and gas wells in the Gulf of Mexico to demonstrate the success of the design.
Oilwell casing perforation has been used in the industry since 1932 and was pioneered by the Lane-Wells Company who introduced the bullet-gun perforating technique. Shortly after the introduction of the bullet gun, explosive jet perforators were introduced, which provided a different and more aggressive way to perforate casing.With the increased demand for oil and gas over the past decades, operators have been forced to explore deeper, hotter reservoirs to find the most prolific reservoirs. These deepwater opportunities have required constant changes to equipment and services to increase their technical capabilities for performing in more critical environments. Perforating with higher-shot densities, propellants, and larger perforating guns has been ongoing to meet these new challenges.A major problem with these increases, however, is the difficulty in predicting dynamic wellbore behaviors that cause tubulars to collapse and bend and packers to unset as perforating guns were detonated. Research to understand the pressure behavior during the perforation event, in addition to the solid loading that is imparted to the tubulars, packers, and other completion hardware in the perforating assembly, was needed to enable the industry to go forward with a high level of confidence that wells could be completed safely and cost effectively.This paper discusses a shock-wave computer modeling program that evaluates the mechanical risk factors of well components to ensure that the health, safety, environment, and service quality needs in a design are addressed. A timemarching, finite-differences technique is applied as the numerical method for both fluids and solids. The software is installed on a personal computer and typically executes the models within several minutes to several hours, depending on the complexity of the job design.The physics-based model has been validated (Schatz et al. 1999 andSchatz et al. 2004) with special high-speed recorders that sense pressure, temperature, and acceleration at a sampling frequency of 115,000 samples per second.This paper provides data from offshore oil and gas wells in the Gulf of Mexico to demonstrate the success of the design.
Many large wells have been drilled in the Gulf of Mexico's Lower Tertiary play. These wells are completed with single-trip multizone systems, and they have gross perforated lengths exceeding 1,500 ft. The main difficulty in perforating these wells is the high-pressure environment (~20,000 psi). Under these conditions, the challenges are to create sufficiently large entrance holes in the casing, minimize the high-risk of equipment damage due to gunshock, and minimize the amount of perforating debris created. Perforating several intervals in a single run is required to complement single-trip multizone systems. Perforating all zones simultaneously in one trip saves time and reduces risks when compared with stacked completions requiring multiple trips for each zone. Safety and cost reduction are extremely important in deepwater operations. Risk control is very important because gunshock and/or debris problems can lead to multimillion dollar losses in non-productive time, and in extreme cases, gunshock problems can lead to lost wells. To undertake these challenges, a new Low Perforating Shock and Debris (LPSD) gun system was used. In comparison with standard high-pressure guns, the LPSD gun system produces much less gunshock and negligible amounts of debris; thus, minimizing gunshock risk and reducing cleanup runs typically needed to recover perforating debris. LPSD guns produce negligible amounts of debris because LPSD guns contain all the metallic components, including the shaped charge cases, which remain virtually intact inside of the guns. A key element in planning these perforating jobs is gunshock prediction to evaluate if the equipment will be able to withstand the transient loads produced by the perforating guns. The gunshock prediction process is described in detail in this paper. For a typical 4-zone 1,500 ft gross length perforating job, the time needed from picking up the first gun to laying out the last gun averages 84 hours. All zones are simultaneously perforated, which eliminates three perforating runs per well, saving approximately 9.2 days per well while minimizing personnel exposure. By perforating the largest high-pressure wells in the Gulf of Mexico's Lower-Tertiary play with LPSD guns, we minimized personnel exposure, minimized debris and reduced execution time up to 72%.
The largest deepwater wells in the Gulf of Mexico have been drilled in the Lower Tertiary play. Most of these wells are completed with single-trip multizone systems have gross perforated lengths exceeding 1,500 ft. The main difficulty in perforating these wells is the ~20,000 psi high-pressure environment. Under these conditions, the challenges include creating sufficiently large entrance holes in the casing, minimizing the high-risk of equipment damage due to gunshock, and reducing the amount of perforating debris created. Perforating several intervals in a single run is required to complement single-trip multizone systems. Perforating all zones simultaneously in a single trip saves time and reduces risk when compared with stacked frac-pack completions requiring multiple trips for each zone. Safety and cost reduction are extremely important in deepwater operations. Risk control is very important because gunshock and/or debris problems can lead to multimillion dollar losses in nonproductive time, and in extreme cases, gunshock problems can lead to lost wells. To undertake these challenges, a new Low Perforating Shock and Debris (LPSD) gun system was used. In comparison with standard high-pressure guns, the LPSD gun system produces much less gunshock and negligible amounts of debris; thus, minimizing gunshock risk and reducing cleanup runs typically needed to recover perforating debris. LPSD guns produce negligible amounts of debris because LPSD guns retain all the metallic components inside the guns, including the shaped charge cases, which remain virtually intact inside of the guns. A key element in planning these perforating jobs is gunshock prediction to evaluate if the equipment will be able to withstand the transient loads produced by the perforating guns. The gunshock prediction process is described in detail in this paper. For a typical 4- to 6-zone 1,500 ft gross length perforating job, the time needed from picking up the first gun to laying out the last gun averages 84 hours. All zones are simultaneously perforated, which eliminates at least three perforating runs per well, saving approximately 9.2 days per well while minimizing personnel exposure. By perforating the largest deepwater high-pressure wells in the Gulf of Mexico's Lower-Tertiary play with LPSD guns, we minimized personnel exposure, minimized debris and reduced execution time up to 72%.
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