Over the last two decades there have been many developments enabling accelerated growth in horizontal drilling. Drilling has been the primary driver, with current technology capable of drilling laterally through a hydrocarbon reservoir for thousands of feet. The second driver has been the completion and stimulation advancement. Initially horizontal drilling was limited to naturally fractured reservoirs with simple open hole or slotted liner completions. This was due primarily to the ability of the reservoir to flow economically without the need for stimulation. Reservoirs requiring stimulation were typically not candidates for horizontal drilling. With developments in completion and stimulation technology, applications for horizontal drilling now encompass a broader range of reservoirs.
Until recently there have been two completion and stimulation option. The horizontal can be completed open hole, or with slotted or perforated liner. This has essentially negated any effective stimulation along the entire length of the horizontal wellbore. The second completion system requires cementing the production liner and running multiple isolation systems to effectively treat different sections of the wellbore. This requires multiple coiled tubing trips along with multiple rig up and rig down of the stimulation equipment involved. These multi-stage horizontal completions take weeks to complete at high cost and elevated risks. Ultimately, the high completion costs or the lack of production due to ineffective stimulation make many reservoirs uneconomical to exploit.
This paper will detail a new completion system which is run as part of the production liner, which does not require cementing and provides positive mechanical diversion at specified intervals, so fracturing and stimulations can be pumped effectively to their targeted zone. Details of the engineering design and testing will be specified, with elaboration on the applications and case histories where these systems have been successfully deployed. The case histories will detail the operational efficiencies of the system in conjunction with the enhanced production realized.
Horizontal drilling has been steadily growing for well over a decade and in many cases has become the exploitation method of choice for infill drilling and reservoir depletion. As successful as horizontal drilling has been, there have been significant technology gaps hampering growth in certain applications. These are applications where fracturing or stimulating the reservoir is necessary to proliferate production to desired levels. For example, matrix sandstone and carbonate reservoirs often require fracturing or stimulation to promote production to levels the reservoir is capable. Without stimulation or fracturing horizontal wells in these types of reservoirs, production is often only equivalent to or slightly higher than the vertical stimulated counterpart, thus not justifiable to the added expense of drilling horizontally. For cased and cemented liner applications this issue was addressed some years back by limited entry techniques and then later by the use of bridge plugs set on coiled tubing (CT), followed byperforating and then stimulating the well. The cement provides the mechanical diversion in the annulus and the bridge plug provides the mechanical diversion in the liner. This process is then repeated for the number of stimulations desired for the horizontal wellbore. (Figure 1)
