Abstract

Drilling long horizontal and multilateral wells with very low drawdown makes efficient cleaning and stimulation treatments very challenging. None of the conventional chemical cleaning methods can overcome problems for filter-cake removal in long horizontal and maximum reservoir contact wells because of limitations such as the complex geometry of wells, nonuniform chemical distribution, low contact between cleaning fluids/filter cake, and high chemical reaction rate, especially at high temperatures.

All of these challenges lead us to develop a new system of filter cake removal method that addresses several key problems inherent in the removal of drilling fluid filter cake, cleaning, and stimulation treatments of horizontal and multilateral wells. This system is a water-based drilling fluid that is weighted with calcium carbonate and has a mixture of solid-acid precursor and particulate solid-acid reactive material. This fluid has both functions of drilling and completion and can reach total depth of MRC wells. It has the ability to effectively stimulate the whole horizontal sections after drilling.

Previous work by the authors on this self-destructing drilling fluid system resulted in obtaining the best formula based on the original water-based mud (SPE 136400). High temperature high pressure filter press results (SPE 139087) showed high filter cake efficiency in cleaning the filter cake. Unlike the conventional reactive acids such as HCl, the slow reaction kinetics ensured good distribution of the generated acid across the filter cake.

The objective of this study is to determine the homogeneity of the self-destructive filter cake. Image J software and Grabit software combined with CT scan results were used to determine the filter cake properties such as porosity, permeability and thickness of the self-destructing filter cake system.

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