Complex barite filter cake removal using in-situ generated acids by thermochemicals

Badr S Bageri,Mohamed Mahmoud,Ayman Al-Nakhli,Shirish Patil,Ibrahim Gomaa

doi:10.1038/s41598-020-72858-y

Badr S Bageri, Mohamed Mahmoud + Show 3 more

Open Access

https://doi.org/10.1038/s41598-020-72858-y

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Abstract

In sandstone formations, the quartz particles integrate with drilling fluid solids and become part of the filter cake structure. As a result, the dissolution rate of the filter cake diminishes and reduces the removal efficiency. This paper presents a novel solution to overcome the challenges that restricts the filter cake removal process such as the presence of the quartz layer and the polymer coat. A multi-stage method for removing the filter cake from a wellbore is presented. The composition of the new formulation is; ammonium fluoride (NH4F), with a strong oxidizer, such as sodium bromate (NaBrO3) causes an exothermic reaction in the first stage, thereby removing the quartz layer and polymer coat in the filter cake by the in-situ generated HF acid. During the second stage for the barite-based filter cake, chelating agents combined with convertor catalysts were used to dissolve the barite. Solubility experiments were conducted to evaluate the efficiency at each stage in the filter cake removal process at 300 ºF and 500 psi. The experimental results showed that the formulation consisting of ammonium fluoride (NH4F), with a strong oxidizer (sodium bromate,NaBrO3), combined with exothermic reaction was able to generate HF in-situ, which in turn dissolved the quartz mineral and remove the polymer from the filter cake.

Highlights

In sandstone formations, the quartz particles integrate with drilling fluid solids and become part of the filter cake structure
An ideal filter cake should be completely impermeable in order to prevent fluid losses to the formation[3,5,12]. It is recommended for the filter cake thickness to be less than or equal to 0.16 of the wellbore diameter to be removed sufficiently by one pore hole volume (PHV) of the filter cake s olvent[13,14]
The collected solids from the filter cake were placed in a Teflon liner cell submerged in the in-situ generated HF acid as the first stage of filter cake removal process

Summary

Introduction

In sandstone formations, the quartz particles integrate with drilling fluid solids and become part of the filter cake structure. The composition of the new formulation is; ammonium fluoride (NH4F), with a strong oxidizer, such as sodium bromate (NaBrO3) causes an exothermic reaction in the first stage, thereby removing the quartz layer and polymer coat in the filter cake by the in-situ generated HF acid. The experimental results showed that the formulation consisting of ammonium fluoride (NH4F), with a strong oxidizer (sodium bromate,NaBrO3), combined with exothermic reaction was able to generate HF in-situ, which in turn dissolved the quartz mineral and remove the polymer from the filter cake. An ideal filter cake should be completely impermeable in order to prevent fluid losses to the formation[3,5,12]. The use of enzymes or the chelating agents are possible chemical methods for removing the filter cake[13,18,19]

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