Drilling-Hazard Mitigation-Reducing Nonproductive Time by Application of Common Sense and High-Value-Well Construction Techniques

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractMitigating drilling hazards-balancing drilling risks against the optimum well design while preparing for unplanned drilling events-has been a challenge to cost-effective well construction for decades. The pore pressure/formation fracture gradient balancing challenges mixed with the unexpected encounters with shallow flows, unstable formations, overpressure formations and depleted formations makes AFE (authorization for expenditures) goals dim.Excessive use of loss circulation pills and traditional contingency liners drive well costs up and jeopardize reaching total depth (TD) with an effective completion. A drilling hazard remediation solution could be as simple as using that planned contingency liner or using drill-in casing to fight sloughing formations. However, the use of conventional solid expandable drilling liners can drive excessive risks into the well and even cause a costly sidetracking of the well.Operators in the Gulf of Mexico, the North Sea and in Asia Pacific have been successfully using a set of proven well construction tools with a more "Fit for Purpose" application to mitigate drilling problems that have resulted in excessive nonproductive time (NPT) during drilling operations. These systems are used only when necessary to mitigate the well challenge, allowing the well construction to continue while minimizing their NPT fighting these well problems.This paper describes some of these "fit for problem" well construction tools and their applications in recent case histories.

Modeling Lost-Circulation into Fractured Formation in Rock Drilling Operations

“…v r,plug , and v r,free are, respectively, the flow velocities within the plug-and free-region. The no-slip boundary condition is described by the last equation in (5).…”

“…Drilling fluid-loss is a costly problem. This phenomenon may obstruct operations, increase the nonproductive time (NPT), contaminate water tables, and cause formation damage and safety hazard [2][3][4][5][6][7][8][9]. Drilling fluid typically accounts for 25-40% of the total drilling costs [8].…”

“…Such problems cost the industry about one billion US dollars per annum worldwide [11,12]. For instance, a study including 1500 gas wells in the Gulf of Mexico showed that lost-circulation accounts for 13% of the total drilling problems [5], as appears in Figure 1. Another study for 103 wells in the Duvernay area in Canada reported a loss of $2.6 million and 27.5 days of NPT because of lost circulation (Figure 2).…”

“…For instance, more than 35% of drilled wells in a fractured carbonate formation in Iran experienced lost circulation [14]. Similarly, in Saudi Arabia, one-third of the [5], where lost circulation accounts for 13% of the total.…”

Modelo Geomecânico Aplicado À Análise De Estabilidade De Poços Com Ênfase Em Folhelhos

“…Segundo Reid et al, (2006), o gráfico da profundidade versus tempo do poço nem sempre representa o tempo programado de perfuração, pois a ocorrência dos eventos de perfuração em zonas problemáticas geram TNP. Na Figura 3.4, observa-se como a ocorrência do TNP influi nas curvas de perfuração, destacando uma parcela onde ocorre a perda "invisível" do tempo (uma redução da eficiência da perfuração), e outra parcela onde é representado o tempo utilizado para tal zona problemática.…”