Wellbore operations using a multi-tube system

A method of completing or stimulating a portion of a wellbore comprising: introducing a treatment fluid into the wellbore, wherein the treatment fluid comprises a base fluid and an insoluble particulate, wherein the treatment fluid flows through a first tube or set of tubes of a multi-tube system during introduction, wherein the multi-tube system comprises multiple tubular members rigidly attached to each other along the axial lengths of the members, and wherein the attached tubular members complimentarily create a cross-sectional shape of a generally D- or wedge-shaped portion of a circle; possibly creating one or more fractures in a subterranean formation; depositing at least a portion of the particulate within the wellbore; and returning at least a portion of the base fluid to a wellhead of the wellbore, wherein the treatment fluid flows through a second tube or set of tubes of the multi-tube system during return.