Abstract

The development of Vaca Muerta has presented significant challenges in the unconventional oil industry. These challenges extend beyond the complexity of drilling and completing several-kilometer-long horizontal branches, as they also include the issue of well-to-well interference due to fractures, known as "frac hits". The primary objective of this case study is to document the series of frac hit events occurring between 2018 and 2023 in a Vaca Muerta field (oil window with multilanding development), analyzing the consequences such as pressure increases or sand production in offset wells, and presenting strategies to mitigate these issues. Additionally, the methods used to forecast these events and estimate potential production losses or well damages will be described. To study frac hits, wellhead flowing pressure (WHFP) obtained through telemetry was analyzed, and a machine learning model was employed to transform WHFP into bottomhole flowing pressure (BHFP) to correlate with production controls and water tracers. A statistical study was conducted, highlighting changes in production (oil and water) and pressure in the offset wells during these events. Furthermore, cases of sand production, effects on water production in the source wells, potential damages to the offset wells, and the influence on well decline after a frac hit were evaluated. Using these statistics, it is possible to predict which wells are susceptible to experiencing frac hits and estimate their intensity. The obtained results revealed that in the mentioned Vaca Muerta field, frac hits represent one of the most significant challenges for its development. Adverse effects were observed, including sand production, casing deformations, considerable oil production losses, and an increase in the production decline of offset wells. Additionally, difficulties in managing large volumes of produced water due to the frac hit were identified. It was observed that second-line receivers present considerably smaller effects compared to first-line receivers, that frac hits can occur between landings only in certain cases, and it was found that clustering numerous fractures using diversion technology amplifies the effects of frac hits, potentially impacting wells located over 1400m away. Through this study, it is possible to estimate frac hit events, considering various factors such as proximity to the source well, BHFP of the offset well, degree of overlap between both wells, among others. Based on this information, quantitative estimations of the duration of the frac hit, oil losses, water production, time required for the bottomhole pressure to return to its pre-frac hit state, and other relevant aspects were made. Measures were implemented to mitigate the consequences of frac hits, such as pressure barriers between the fractured wells and offset wells, securing neighboring wells, opening the size of choke to facilitate water drainage, and reducing the size of choke in case of sand production.

This content is only available via PDF.
You can access this article if you purchase or spend a download.