Dynamic Underbalance Perforating for Production Enhancement and Frac Optimization in Tight Gas Wells: Case Study from Sultanate of Oman

Abstract

Abstract The objective of the paper is to demonstrate the effectiveness of the dynamic underbalance (DUB) perforation technique, especially in enhancing the performance of deep tight gas wells in the Sultanate of Oman. The technique aims to provide cleaner perforation tunnels, eliminate perforation damage, and improve flow/injection by creating a sharp, localized pressure drop across the perforation interval immediately after the perforation tunnels are formed. The paper begins with an overview of the operation and the nature of the deep tight gas wells in the field, with particular emphasis on the tight reservoir with low permeability. It underlines the importance of combining deep penetration jet charges with dynamic underbalance (DUB) to achieve deep and clean perforation tunnels which helps in reducing the perforation skin and improving connectivity with the reservoir, contributing significantly to optimizing the hydraulic fracturing job that results in lower breakdown pressure and more successful frac placement. This paper presents field examples where the dynamic underbalance (DUB) technique was applied in multiple tight gas wells. Details include the use of a 2 7/8" gun configuration in 4.5" completion size with a fast pressure gauge run alongside the perforation gun to measure the extent of dynamic underbalance created by the gun system. These actual measurements were then compared with estimated dynamic underbalance values derived from pre-job simulations using proprietary software. The results largely mirrored the predictions, indicating the effectiveness of the modeling process. In most cases, we observed a reduction in the treating pressure required for fracturing. Despite high formation stresses in some wells which limited the impact of DUB, a great improvement in initial production rates was observed, compared to projected rates. The results demonstrate the effectiveness of the DP perforation guns with DUB perforating technique in enhancing connectivity with the reservoir, leading to achieve higher production flow rates. This effective performance eliminated the necessity for fracking in the designated zone. Also, the effectiveness extends to the pre-frac perforation application in achieving breakdown and fracture placement in the ultra-strong formations of field B, where rock strength exceeds 30 KPSI. In such challenging formations, conventional gun systems often struggle to initiate breakdown pressure in these formations and abrasive jetting with coiled tubing has typically been utilized to initiate fracturing in this environment however, it is costly, big footprint and much less efficient. The adoption of DP perforation with DUB technique has substantially enhanced both efficiency and cost savings.