Determining the Magnitude of Interference Among Adjacent Wells in a Saudi Arabian Unconventoinal Formation

Abstract

Gaining an understanding of the well to well interference during hydraulic fracturing and subsequently production interference is paramount in optimizing the costs associated with field development. Much work has been done in the industry to better understand the interference during hydraulic fracturing and production among adjacent wells. This paper presents an analysis that employed both a pressure interference analysis and chemical tracer analysis to gain a better understanding of the fracture interference in a well pad in the Jafurah field. The subject pad consists of 4 wells. Two of which run parallel in a north direction and the other two run parallel in the southern direction. All four wells were hydraulically fractured with slickwater design. Adjacent to the subject pad is another pad that had been previously stimulated with crosslink design and was used for pressure monitoring. The distance between the laterals was relatively similar (X ft) with one exception (2 × ft). Initially, one well from both directions was stimulated with 33 stages each of slickwater design and the plugs were subsequently milled out. Afterwards, the other two wells were stimulated with 33 stages of slickwater each. In 7 of the 33 stages of the later wells, 20 oil and 20 water tracers were injected in sequence in an attempt to study the physical extent of the fractures generated. While the latter two wells were being stimulated, the wellhead pressure on the parallel wells was being monitored and recorded along with the wellhead pressures on the adjacent pad. During flowback, the southern wells were flowed back simultaneously and flowback samples were collected to be analyzed for tracers. Subsequently, the northern wells were opened up to flowback in the same manner and flowback samples were also collected for tracer analysis. Wellhead pressure was monitored on the adjacent pad during flowback of all the wells. The pressure data during the fracturing operation indicated for distance × ft and the size of stimulation stages pumped, a level of communication which was further verified by the production interference analysis as well as the tracer data.

The Effect of Hydraulic Fracture Geometry on Well Productivity in Shale Oil Plays with High Pore Pressure

“…Similarly, hydraulic treatments in the Jafurah Basin in Saudi Arabia require large fracturing fluid volumes and proppant amounts. From published data, we deduce that total fracturing fluid volumes and proppant mass per wellbore are about 18,000 m 3 (∼113,000 bbls) and 3600 tons (∼7.2 MM lbs) [44,45,47,81]. The average horizontal wellbore length in the Jafurah basin is approximately 1500 m (∼5000 ft) [45,53].…”

“…The contribution of the exterior flow to the stimulated reservoir volume is minimal because we only consider the reactivation of natural fractures near the stimulated hydraulic fractures, and the matrix has ultra-low permeability [41]. Based on the reported massive stimulation jobs performed in mudrock plays worldwide [44][45][46][47][48][49], we estimate a total fracturing fluid volume injected into the rock of 12,700 m 3 (∼80,000 bbls) distributed evenly among the 22 stages. We consider the same fracturing fluid volume for all fracture scenarios and predetermine the stimulated volume's geometry based on each scenario.…”