Sand or Mud Removal in Low Bottom Hole Pressure Wellbores Using Jet Pump and Concentric Coiled Tubing Leads to Improved Production

Abstract

Horizontal drilling and completion are common practice for accessing conventional and heavy oil reservoirs. During the drilling process, the formation pore pressure is less than the drilling fluid's hydrostatic pressure. This can lead to some fluid loss before a filter cake is formed to prevent further mud losses. For unconsolidated formations, it is prefer to keep the filter cake in the place to maintain the hole's integrity during the well completion period while running the liner. However, the filter cake can be broken down by the sliding and rotating of the bottom hole assembly. These breakdowns can lead to high completion fluid losses to the formation. Sand production is also a common problem associated with unconsolidated formations. These drilling & completion practices, sand production, have resulted in a demand for well intervention that can economically remove mud damage and produced fill throughout the whole length of horizontal wells. Since 1995, a technology combining concentric coiled tubing (CCT) with a jet pump has been developed and used to remove both the drilling fluids, filter cake and solids. Initially it was developed for horizontal heavy oil reservoirs where pressures are low and oil viscosity is high, without placing hydrostatic loads on the reservoir. The job data from more than 600 sand/well vacuuming operations worldwide has been compiled into a database. This paper reviews the well information and the key operating parameters: maximum depth, bottom hole pressure gradient and pump rate. The engineering challenges, best practices and lessons learned from the sand/well vacuuming process are also summarized. Analysis of this data yields a better understanding about the vacuuming technology and provides good guideline for future operations. Case histories are provided demonstrating how to deploy the different sand/well vacuuming bottom hole assemblies (BHA) for different applications. Post job analysis indicates CCT vacuuming technology reduces the skin damage and increases the production compared to non-vacuumed wells. Moreover, the details estimated from sand and other fluid influx profiles along the wellbore during the vacuuming process, are used to evaluate well production and develop a management strategy. Introduction During the drilling operation of most horizontal heavy oil wells, the drilling fluid hydrostatic column causes fluid loss to the formation due to the low bottom hole pressure (BHP). Otherwise, the presence of the filter cake adhered to the formation face creates an artificial layer between the formation face and the slotted liner, affecting the production from the reservoir, in other words, creating an additional pressure drop from the formation to the wellbore. After the drilling operation is completed, the production pump is run in hole and used to retrieve drilling fluids and the filter cake. The problem with this method is that the suction produced by the production pump is mainly a localised pressure drop in the zones nearest to the pump, without creating significant suction at the toe of the well. Therefore, the well will produce mainly from the heel and will have a lower production contribution from the toe. Sand production is also a common problem faced by many of heavy oil producers worldwide. The slotted liner acts as a partial barrier, grading effects at the slots often still result in sand migration into the wellbore and a low production rate. The low production flow rates contribute to increased deposition of the sand within the highly deviated wellbore.

Pushing the Boundaries of Concentric-Coiled-Tubing Technology To Resurrect Subhydrostatic Gas Wells on an Unmanned Offshore Installation

“…While this technology was proven onshore (Benzaquen et al 2006;Kuchel et al 2002;Li et al 2008a;Hibbeler et al 2002) and in offshore Alaska (Rafferty et al 2007), there had been no application in the North Sea, and there was therefore very limited knowledge of the technology locally. CCTVT consists of a CT string inside CT, where circulated liquid is used to activate a jet pump to suck well fi ll into the CT and circulate it back to surface.…”

Pushing the Boundaries of Concentric Coiled Tubing Technology To Resurrect Sub-Hydrostatic Gas Wells on an Unmanned Offshore Installation

“…The main advantages of this technology are its ability to minimize liquids pumped into the well, its independence of reservoir pressure, and its ability to remove liquid at the end of operations to ensure the well can be returned to production. Whilst this technology was proven onshore 6,7,8,9 and in offshore Alaska 10 , there had been no application in the North Sea, and therefore very limited knowledge of the technology locally. Operational data also showed that the technology had never been applied at the reservoir depths of the Ravenspurn North field, and the additional weight of the concentric coiled tubing was recognized as a challenge with limited crane capacity and deck loading on the small ST3 platform.…”

Utilizing a Micro-Vacuuming Jet Pump and Concentric Coiled Tubing to Clean Mud Damage and Fill from Wellbores with Small Completion Size and Low Bottom Hole Pressure

“…The sand/well vacuuming technology has been developed and proven by field operations [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] worldwide to clean out wellbores with a low bottom hole pressure. The sand/well vacuuming technology has been developed and proven by field operations [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] worldwide to clean out wellbores with a low bottom hole pressure.…”