Lost-circulation diagnostics using derivative-based type-curves for non-Newtonian mud leakage into fractured formation

TL;DR

This paper introduces a semi-analytical model with derivative-based mud-type-curves for rapid diagnosis of lost circulation of non-Newtonian fluids in fractured formations, improving accuracy and reducing non-uniqueness in predictions.

Contribution

It develops novel dual type-curves and a dual trend matching method for better diagnostics of fluid leakage, incorporating non-Newtonian fluid behaviors and uncertainty analysis.

Findings

Effective fracture conductivity can be estimated from transient pressure data.

The model accurately predicts mud-loss volume and leakage duration.

Field data demonstrates the method's practical applicability.

Abstract

Drilling is a requisite operation for many industries to reach a targeted subsurface zone. Loss of circulation is a common problem that often causes interruptions to the drilling process and a reduction in efficiency. In this work, a semi-analytical solution and mud type-curves (MTC) are proposed to offer a quick and accurate diagnostic model to assess the lost-circulation of Herschel-Bulkley fluids in fractured media. Based on the observed transient pressure and mud-loss trends, the model can estimate the effective fracture conductivity, the time-dependent cumulative mud-loss volume, and the leakage period. The behavior of lost-circulation into fractured formation can be quickly evaluated, at the drilling site, to perform useful diagnostics, such as the rate of fluid leakage, and the associated effective fracture hydraulic properties. Further, novel derivative-based mud-type-curves (DMTC) are developed to quantify the leakage of drilling fluid flow into fractures. The developed model is applied for non-Newtonian fluids exhibiting yield-power-law, including shear thickening and thinning, and Bingham plastic fluids. Proposing new dimensionless groups generates the dual type-curves, MTC and DMTC, which offer superior predictivity compared to traditional methods. Both type-curve sets are used in a dual trend matching, which significantly reduces the non-uniqueness issue that is typically encountered in type-curves. Data for lost circulation from several field cases are presented to demonstrate the applicability of the proposed method. The semi-analytical solver, combined with Monte Carlo simulations, is then applied to assess the sensitivity and uncertainty of various fluid and subsurface parameters. The proposed can serve as a quick diagnostic tool to evaluate lost-circulation in drilling operations.