The flow of homogeneous fluids through porous media: analogies with other physical problems

An analytical model to couple gas storage and transport capacity in organic matter with noncircular pores

Wellbore stability in naturally fractured formations featuring dual-porosity/single-permeability and finite radial fluid discharge

Prediction of methane adsorption in shale: classical models and machine learning based models

Mechanical characteristics of well cement under cyclic loading and its influence on the integrity of shale gas wellbores

Cuttings Settling and Slip Velocity Evaluation in Synthetic Drilling Fluids

Quemada model approach to oil or synthetic oil based drilling fluids rheological modelling

\n The occurrence of reversible mud losses and gains while drilling in naturally fractured formations (NFFs) is of primary concern. Borehole breathing can complicate the already difficult practice of fingerprinting the changes in the return-flow profile, hence undermining the reliability of kick detection. Issues can also derive from misdiagnosing a kick and attempting to kill a breathing well. The objective of this work is to correctly address the phenomenon and increase insights regarding its physical characterization. The fluid progressively flows in and out of fractures as a consequence of three mechanisms: bulk volume deformation, fluid compressibility, and fracture-aperture variation. To represent this complex scenario, a model involving a continuously distributed fracture network is developed. A time-dependent, 1D dual-poroelastic approach is coupled with a variable fracture aperture and a passive porous phase. Finite fracture network length is considered, and no limitation on the number of fractures is posed. The latter permits us to analyze long openhole sections intersecting several fissures, which is a more realistic approach than the available single-fracture models. The proposed model is able to quantify pressure distribution in fractures and pores, together with the flow rate entering or exiting the fractures. Furthermore, a useful application of the model is proposed by suggesting its application as a breathing discriminator during kick diagnosis. The shut-in drillpipe pressure (SIDPP), recorded from a real kick, has been compared with one caused by a simulated breathing case. Although the two SIDPPs show significant similarities, the correct modeling of breathing can help the identification of the major differences between a kick and breathing.

A Novel Approach to Borehole-Breathing Investigation in Naturally Fractured Formations


 In most drilling environments, wellbore pressure exceeding the fracture–opening/initiation gradient often results in major fluid losses when drilling ahead and fluid returns when circulation is stopped. The phenomenon is generally referred to as wellbore breathing. Because no flow is expected when circulation is stopped, the mudflow return is more noticeable and could lead to kick misdiagnosis. To rapidly identify whether a possible influx is caused by formation breathing (or otherwise), correct interpretation and modeling of this phenomenon are paramount. The latter can be used to generate a reliable diagnostic tool for breathing discrimination, and it can also be turned into a valuable resource. Potentially, several in–situ properties of the fractured formation can be inferred with static flowback signatures and pressure–while–drilling (PWD) data. This paper shows how to use the proposed geomechanical model to generate diagnostic flowback type curves. A step–by–step procedure is then presented to discriminate the nature of the influx and to infer the fracture–network properties (damaged radius, generalized hydraulic diffusivity, average borehole breathability, and generalized total compressibility) through a type–curve matching protocol. Several field data have been analyzed to show the applicability of the proposed diagnostic tool and to validate its ability to rapidly differentiate borehole breathing from a kick.

Silvio Baldino

Papers

Wellbore stability in naturally fractured formations featuring dual-porosity/single-permeability and finite radial fluid discharge

Cuttings Settling and Slip Velocity Evaluation in Synthetic Drilling Fluids

Quemada model approach to oil or synthetic oil based drilling fluids rheological modelling

A Novel Approach to Borehole-Breathing Investigation in Naturally Fractured Formations

Borehole-Breathing/Kick Discriminator: Diagnostic Tool and Potential Resource for In-Situ Formation Characterization