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

摘要

The Jean Marie reservoir in the northeastern part of BritishrnColumbia, Canada, is one of the most active horizontallyrnunderbalanced drilled reservoirs in the world. The Jean Mariernis a depleted, low permeability, fractured carbonate with lowrninitial water saturation making it susceptible to formationrndamage using conventional drilling fluids. Given thesernreservoir characteristics, horizontal underbalanced drilling isrnthe current method of choice for operators active in the area.rnAlthough underbalanced technology has made tremendousrnimprovements in maintaining and ensuring underbalancedrnconditions at all times during operations, overbalancedrnincidents do occur while drilling the horizontal section. Thesernincidents can be much more damaging than drilling with arnwell designed overbalanced fluid. In some cases, anrnoverbalanced event could permanently impair production fromrna well by as much as 75%.rnWith the aid of real time downhole pressure gauges, thesernoverbalanced incidents can be identified but very often gornundetected, leading to a false sense of achieving the goal ofrnminimal damage. The unidentified damage can lead tornmisinterpretation of production results and disappointmentrnwith underbalanced drilling.rnTo exacerbate the problem of identifying damage,rntraditional pressure transient analysis of wells in the JeanrnMarie may yield incorrect valuation of the overbalancedrnincidents by underestimating the skin on the face of thernhorizontal well. This could be due to the difficulty ofrnperforming meaningful transient analysis on a horizontal wellrnin a dual porosity reservoir and a general lack of knowledge ofrnthe impact of drilling related damage on fractured or highlyrnheterogeneous reservoirs.rnThis paper will show how, by combining transientrnproductivity index data collected while drilling with the use ofrnhistory matching techniques, overbalanced incidents can berneasily identified and the impact on well productivity can bernquantified.