Wellbore Strengthening Design Criteria and Enhanced Fracture Gradient for Widening Stable Mud Weight Window and Enabling Safe and Efficient Drilling in Depleted Reservoirs

Drilling in permeable formations, especially depleted reservoirs, can particularly benefit from simultaneous wellbore shielding and strengthening functionalities of drilling mud compounds. The ability to generate simultaneous wellbore shielding and strengthening in reservoirs has potential to widen stable mud weight windows to drill such reservoirs without the need to switch from wellbore strengthening compound to wellbore shielding compound, and vice-versa. Wellbore shielding and strengthening experiments were conducted on three outcrop sandstones with three mud compounds. The wellbore shielding stage was conducted by increasing the confining and borehole pressures in 4-5 steps until both reached target pressures. CT scan images demonstrate consistency of the filtration rates with observed CT scanned mud cakes which are dependent on the sandstone pore size and mud compound particle size distributions. In wellbore strengthening stage, the borehole pressure was increased until fracture was initiated, which was detected via borehole pressure trend and CT scan imaging. The fractures generated were observed to be plugged by mud filter solids which are visible in the CT scan images. The extent of observed fracture solid plugging varies with rock elastic properties, fracture width and mud compound particle size distribution. Based on the laboratory test data, fracture gradient enhancement concept was developed for the mud compounds. In addition, the data obtained and observations from the tests were used to develop optimal empirical design criteria and guidelines to achieve dual wellbore strengthening and shielding performance of the mud compounds. The design criteria were validated on a well which was treated with one of the mud compounds based on its mud loss events during drilling and running casing.

OH + OKAY in informing sequences: On fuzzy boundaries in a particle combination

This study explores fuzzy boundaries, or weak cesuras, in the particle combination OH + OKAY as used in informing sequences in ordinary English talk-in-interaction. The focus is on the third position in such sequences, where OH + OKAY responds to information that has been solicited by the speaker in a prior turn. Based on a collection of approximately 45 instances of OH + OKAY in recent American English telephone and face-to-face interactions, this study adopts the methodology of Conversation Analysis and Interactional Linguistics to examine the prosody and phonetics of OH + OKAY as a feature of turn design. It asks: (i) when does the speaker use a combination of OH and OKAY in the third position rather than a simple OH or OKAY? and (ii) to what extent does the prosodic–phonetic delivery of OH + OKAY contribute to an interpretation of what the turn is doing? The study finds that (i) OH + OKAY is used when responding to a solicited informing that not only supplies information but also accomplishes another action with consequences for the recipient and (ii) if OH + OKAY is delivered with a strong cesura between its parts, its actions are distributed in separate turn-constructional units, creating a multi-unit turn that proposes sequence closure. If the cesura in OH + OKAY is weak, the component parts are fused into a compound particle that can preface more talk by the same speaker. Weak boundaries between OH and OKAY can be exploited by participants for the purposes of turn construction and epistemic positioning.

Dynamics and stability of a concentric compound particle – a theoretical study

Particles confined in droplets are called compound particles. This work investigates the dynamics and stability of a concentric compound particle under external forces and imposed flows.