Junction isolation apparatus and methods for use in multilateral well treatment operations

For use in a subterranean well having a first wellbore and a second wellbore extending outwardly from the first wellbore at a junction between the first and second wellbores, apparatus operatively insertable into the well to create therein a fluid flow passage sealingly straddling the junction, the apparatus comprising:

• an elongated first generally tubular structure having first and second longitudinally spaced apart portions with first and second external sealing devices respectively disposed thereon, the first external sealing device being sealingly engageable with an interior surface portion of the first wellbore, and the second external sealing device having an outer surface through which a recess inwardly extends to the first structure;
• an elongated second generally tubular structure coaxially, sealingly and removably received in the first tubular structure;
• and
• a seal test fluid flow passage extending from the interior of the second structure into the recess in the second external sealing device.

Subterranean well apparatus comprising:

• a first wellbore;
• a second wellbore extending outwardly from the first wellbore at a junction between the first and second wellbores;
• and
• a generally tubular structure having upper and lower ends, a fluid flow path interiorly extending longitudinally through the structure between its open upper and lower ends, an upper end portion sealingly and removably engaging a first interior area of the first wellbore uphole of the junction, and a lower end portion sealingly and removably engaging a second interior area of a selected one of (1) a portion of the first wellbore downhole from the junction and (2) a portion of the second wellbore to cause the fluid flow path to sealingly straddle the junction,
• the open upper end of the structure communicating the fluid flow path with substantially the entire cross-sectional area of an upwardly adjacent longitudinal portion of the first wellbore in a manner such that a treatment fluid may be flowed directly through substantially the entire cross-sectional area of the upwardly adjacent longitudinal portion of the first wellbore and into the selected wellbore portion, via the fluid flow path, without fluid recirculation from the selected wellbore portion.

For use in a subterranean well, a method of isolating a junction between a first wellbore and a second wellbore extending outwardly from the first wellbore, the method comprising the steps of:

• providing an elongated assembly including an outer, generally tubular structure having upper and lower longitudinal portions, and an inner, generally tubular structure coaxially and removably received in the outer structure, the lower longitudinal portion Of the outer structure having an external sealing device thereon;
• positioning the assembly in the well with the upper longitudinal portion of the outer structure disposed within a first area in the first wellbore uphole of the junction, and the external sealing device being sealingly engaged with a second area of a selected one of (1) a portion of the first wellbore downhole from the junction and (2) a portion of the second wellbore;
• testing the external sealing device by flowing a seal test fluid in a downhole direction through the inner structure and outwardly through the sealingly engaged external sealing device;
• and
• creating a seal area between the upper longitudinal portion of the outer structure and the first area in the first wellbore.

A method of treating a subterranean well having a first wellbore and a second wellbore extending outwardly from the first wellbore at a junction between the first and second wellbores, the method comprising the steps of:

• supporting an elongated, open-ended, generally tubular flow structure within the well, with a first longitudinal portion of the flow structure disposed within a first area of the first wellbore uphole of the junction, and a second longitudinal portion of the flow structure disposed within a second area of a selected one of (1) a portion of the first wellbore downhole from the junction and (2) a portion of the second wellbore, the first longitudinal portion of the flow structure having a substantially greater flow area that that of the second longitudinal portion;
• causing the flow structure to define a fluid flow path sealingly straddling and isolated from the junction by forming a first seal between the flow structure and the first area and forming a second seal between the flow structure and the second area;
• and
• flowing a pressurized well treatment fluid sequentially in a downhole direction through a tubular supply structure sealingly engaged and in flow communication with the first longitudinal portion and extending therefrom to the surface through the first wellbore, and then into the selected wellbore portion through the flow structure.