Damage Interpretation of Properly and Improperly Drilled Underbalanced Horizontals in the Fractured Jean Marie Reservoir Using Novel Modeling and Methodology

Abstract

fax 01-972-952-9435. AbstractThe Jean Marie reservoir in the northeastern part of British Columbia, Canada, is one of the most active horizontally underbalanced drilled reservoirs in the world. The Jean Marie is a depleted, low permeability, fractured carbonate with low initial water saturation making it susceptible to formation damage using conventional drilling fluids. 1 Given these reservoir characteristics, horizontal underbalanced drilling is the current method of choice for operators active in the area.Although underbalanced technology has made tremendous improvements in maintaining and ensuring underbalanced conditions at all times during operations, overbalanced incidents do occur while drilling the horizontal section. These incidents can be much more damaging than drilling with a well designed overbalanced fluid.In some cases, an overbalanced event could permanently impair production from a well by as much as 75%.With the aid of real time downhole pressure gauges, these overbalanced incidents can be identified but very often go undetected, leading to a false sense of achieving the goal of minimal damage. The unidentified damage can lead to misinterpretation of production results and disappointment with underbalanced drilling.To exacerbate the problem of identifying damage, traditional pressure transient analysis of wells in the Jean Marie may yield incorrect valuation of the overbalanced incidents by underestimating the skin on the face of the horizontal well. This could be due to the difficulty of performing meaningful transient analysis on a horizontal well in a dual porosity reservoir and a general lack of knowledge of the impact of drilling related damage on fractured or highly heterogeneous reservoirs. This paper will show how, by combining transient productivity index data collected while drilling with the use of history matching techniques, overbalanced incidents can be easily identified and the impact on well productivity can be quantified.

Drilling Underbalanced From A Floating Unit In A 1,500-m Of Water Depth Exploratory Well: Planning, Equipment, And Rig Modifications

“…Besides the successful implementation in La Concepción, literature reports other historical cases 9 and theoretical studies 10 supporting that UBD may present better results than conventional overbalanced when dealing with fractured carbonates. The experience in La Concepción was that conventional overbalanced drilling would result in massive loss of circulation which could not be controlled with bridging or sealing mud additives.…”

Fluid Customization and Equipment Optimization Enable Safe and Successful Underbalanced Drilling of High-H2S Horizontal Wells in Saudi Arabia

“…It also reduces or eliminates formation damage because there is no fluid lost to the formation in most cases, resulting in higher productivity wells, and possibly increases reserves. [6][7][8][9][10][11][12][13] More recent techniques in evaluating candidates for underbalanced drilling have removed much of the uncertainty whether a particular well will benefit from UBD 14 , and the development of new equipment and fluids has improved the safety, efficiency and productivity of wells drilled or completed underbalanced.…”