The Importance of Being Well Connected - High Rate Fracs in Horizontals
Authors: Casero A. , Nicolaysen A. , Rylance M. , Clifton J. , Fears B. 
Published: January 2017

In the majority of fractured oil and gas wells, conventional perforating is the typical approach of choice to provide the primary connectivity of fractures to the wellbore, and in horizontal wells the very discrete nature of this connection assumes a significantly higher importance. In multi-fractured horizontal wells, this connection drives the ability to efficiently place the fracture treatments during pumping and the efficiency with which the fracture can subsequently be produced. Consequently, selection of the most appropriate connection technique can be absolutely key to many aspects of a successful implementation of a fracturing campaign.

The use of shaped-charge perforating is quite commonplace and predominantly considered as best practice for the majority of scenarios, in order to establish fracture/wellbore connectivity. However, there are certain situations where such approaches may not provide an efficient solution. This is particularly true in those horizontal wells drilled and completed in complex stress regimes, also in reasonable permeability reservoirs, that have multiphase flow potential or with just a few transverse fractures that are expected to produce at moderate to high production rates from each frac. In these particular cases, a complex connection resulting from perforating can often be detrimental to fracture width creation, making proppant placement challenging and reducing effective fracture conductivity. Additionally, convergent and multi-phase flow behaviour can create extremely high pressure drops in the near wellbore area subsequently impeding the productivity.

While open-hole completions can be one of the methods to deal with this situation, by effectively eliminating the "problem" at source, this is typically delivered at the expense of loss of control on the point of fracture and also with a statistical isolation failure rate. When this is implemented in multistage/multi-cluster frac environments (effectively hundreds of fracs) such statistical failure is an acceptable risk. However, when a single-well frac count is just 3, 4 or 5 per well, any statistical failure can be materially impactful on the well productivity. In those cases when open-hole is not an attractive approach then cased-cemented is preferred, and the application of abrasive jetting can provide an effective alternative to the use of shaped-charges.

This paper will fully describe a suite of tests performed with different shaped-charges as well as abrasive jetting perforators, static holes and dynamic slotting for the multi-fractured horizontal wells in the Khazzan tight-gas condensate field in the Sultanate of Oman. The paper will also include a comprehensive review of multiple injection tests that were performed in both Khazzan vertical and horizontal wells (Al Shueili et al., 2016), through both shaped-charge and abrasive jetted connections. This review will offer observation on maximising the effectiveness of the pre-frac wellbore connection technique in challenging environments.