In recent years, new drilling technologies have changed the traditional wellprofile to increase field productivity. The majority of new wells now being drilled have one or more horizontal legs in order to maximize the drilled hole interface with the rock formation, thereby increasing production from a single wellhead. New techniques to manage and service these wells have also emerged, however, re-entry into open hole or uncontrolled multilateral junctions can be difficult.
A new coil tubing tool or lateral entry guidance system has been developed to help locate and steer into these multiple completions. The tool uses aunique methodology for use with standard coil tubing to gain access into lateral legs. No special electrical conduits are required to operate the tool and tool function is automatic when downhole. A precise series of pressures and flow rates from a surface pump are the only requirement to operate the tool. The tool can deliver most stimulation fluids directly via the coiled tubing orpiggyback other coil tubing tools.
From an economic standpoint, there has always been emphasis on maximizingflow from a given formation while minimizing recovery or well costs. Today, there is growing interest in increasing the contact area of the drilled hole with the formation by drilling multiple legs or laterals in the horizontalsection of the hydrocarbon bearing formation.
This results in maximum wellbore contact area with a minimum of wellhead and surface equipment.
Although this seems an ideal solution to produce a well, a new problem arises. How to achieve well control? Re-entry into these multiple laterals for stimulation or zonal isolation can be a challenge. With cased holes, special junction valves or completion jewellery can be installed to accomplish this side leg re-entry. These junctions, however, can be technically difficult and prohibitively expensive in more marginal fields. This type of junction technology cannot be applied to open hole multilaterals.
This obvious shortcoming led to the development of an original tool design to accomplish multilateral re-entry, especially for open hole. Due to the horizontal nature of these laterals, coiled tubing would seem an obvious stransport device for such special tooling. In fact, existing coiled tubing drilling tools can re-enter these laterals but are over designed, complex and expensive for simple day-to-day well operations.
Therefore, creating a new tool, which makes use of special methodologies or hole geometry to allow for simple and effective running procedures on coiled tubing is needed so that well intervention work can be conducted on individuallegs.
The first step in developing any new tool is to layout goals to be achieved. Obviously, the lateral entry guidance tool needs to select alternate legs with some confidence, as well as provide feedback that it has successfully done so. Additionally, the tool either by itself, or by various methodologies needs to identify which lateral leg it has entered.
The initial inclination of the tool engineer is to design a tool with an electrical line and guidance system. This, however, complicates the tool and makes it more expensive. Typically, electrical conduits are problematic when used with acids, which are likely to be the stimulation fluid most commonly used in conjunction with such a tool.