Combinations of Date Seeds and Rock Salt Systems in Acid Fracturing

Disclosed are compositions and methods for acid fracturing. Specifically, disclosed are compositions and methods for acid fracturing diversion.

Acid fracturing is widely performed as a stimulation technique for carbonate formations in order to improve the productivity of the well. Having an effective stimulation job will improve the productivity of the well. One of the key elements to have an effective stimulation job is the use of diversion system. There are two main types of diversion agents in acid fracturing operations. Near-wellbore diversion and formation diversion. Near-wellbore diversion aims to improves efficiencies of wells by blocking or plugging open fractures or perforations near the wellbore. Near-wellbore diversion is a method that seeks to divert fluids between multiple clusters inside the wellbore, done to target clusters that were not receiving fluids prior to the diversion. Formation diversion is a method where material such as fibers, are pumped within the stimulation schedule to create diversion far inside the formation, and have fluids stimulate further or different sections inside the formation.

Disclosed are compositions and methods for acid fracturing. Specifically, disclosed are compositions and methods for acid fracturing diversion.

In one aspect, a method for isolating perforation clusters in a wellbore is provided. The method includes the steps of injecting a stimulation fluid into the wellbore containing a first perforation cluster and a second perforation cluster, where the stimulation fluid flows into the first perforation cluster and the second perforation cluster is in the absence of flow of the stimulation fluid, injecting a diversion mixture into the wellbore, where the diversion mixture includes date palm seeds, rock salt, and a fluid, where the diversion mixture flows to the first perforation cluster, blocking the first perforation cluster with the date palm seeds and rock salt of the diversion mixture to produce a blockage, where the fluid flows through the first perforation cluster leaving the date palm seeds and rock salt to produce the blockage, and injecting the stimulation fluid into the wellbore, where the stimulation fluid flows into the second perforation cluster.

In certain aspects, the wellbore is a cemented wellbore and the method further includes the step of perforating the cemented wellbore to produce the first perforation cluster and second perforation cluster. In certain aspects, the wellbore includes multiple perforation clusters, where one or more perforation clusters receives flow of the stimulation fluid simultaneously while one or more perforation clusters are in the absence of the flow of stimulation fluid. In certain aspects, the blockage degrades over time such that the first perforation cluster receives flow of the stimulation fluid after the blockage degrades. In certain aspects, the method further includes the step of cleaning the wellbore to remove residue of the diversion mixture. In certain aspects, the date palm seeds are ground date palm seeds having a particle size between 0.15 mm and 5 mm. In certain aspects, the rock salt includes sodium chloride. In certain aspects, the fluid includes an aqueous fluid.

In the accompanying Figures, similar components or features, or both, may have a similar reference label.

While the scope of the apparatus and method will be described with several embodiments, it is understood that one of ordinary skill in the relevant art will appreciate that many examples, variations and alterations to the apparatus and methods described here are within the scope and spirit of the embodiments.

Accordingly, the embodiments described are set forth without any loss of generality, and without imposing limitations, on the embodiments. Those of skill in the art understand that the scope includes all possible combinations and uses of particular features described in the specification.

The composition and methods form a temporary diversion mixture capable of blocking one or more perforation clusters. The composition and methods enable near wellbore fluid diversion by block different perforation clusters. The composition and methods can be used as part of the acid fracturing pumping schedule. Advantageously, the compositions are degradable which allows the isolation to be temporary. Advantageously, the diversion mixture is temporary without the need for intervention. Advantageously, the compositions and methods improve the efficiency of the acid fracturing without increasing the complexity of isolating perforations and clusters of the wellbore. Advantageously, after isolation of perforation clusters is no longer required for effective operation, stimulation fluids can be introduced to remove residue of the perforation mixture for clean-up of the wellbore and near-wellbore.

As used throughout, “rock salt” refers to sodium chloride (NaCl) angular salt. The rock salts can be in various sizes as needed.

As used throughout, “temporary” refers to a time span of hours and specifically the range of 4 to 8 hours.

The diversion mixture includes date palm seeds, rock salt, and a fluid. The diversion mixture can be pumped as a pill.

The date palm seeds can be of any form capable of being used in a wellbore or as part of the diversion mixture. In at least one embodiment, date palm seeds suitable for use in the diversion mixture can have the properties and be prepared by the methods described in U.S. Pat. No. 10,457,846 and U.S. Pat. No. 11,041,347, both of which are incorporated herein by reference in their entirety. The size of data palm seeds used depends on the estimated size of the perforations and fractures in the formation. The date palm seeds can be ground date palm seeds having a particle size in the range of 0.15 millimeters (mm) and 5 mm and alternately between 2 mm and 4 mm. The methods and systems described result in the date palm seeds along with the rock salt plugging the perforations.

The fluid can be any type of use suitable for carrying the date palm seeds and rock salt without immediately dissolving or degrading either. The fluid can be selected based on the desired length of time that the perforation is desired to be isolated. In at least one embodiment, the fluid is an aqueous fluid. In at least one embodiment, the fluid is water. The water can be treated water or fresh water. Advantageously, the use of water reduces or eliminates the likelihood that the materials will dissolve prior to reaching the perforation clusters. The diversion mixture can be pumped with the fluid as a part of the stimulation schedule.

In an acid fracturing operation, the fracturing fluid or stimulation fluid will exit the wellbore through the perforation cluster that leads to the lowest stress zone. As a result, not all perforation clusters will be stimulated simultaneously. When conditions indicate that not all perforation clusters are being simulated simultaneously the diversion mixture can be introduced to the wellbore. The diversion mixture will be drawn to the perforation clusters that lead to the lowest stress zone and due to their size will temporarily plug the perforation tunnels of the perforation clusters. As a result, the fracturing fluid can be redirected to other perforation clusters and stimulate other areas of the formation resulting in increased reservoir contact. Advantageously, the perforation mixture will degrade naturally without the need for intervention allowing stimulation fluids to flow for clean-up and gas flow estimation. Advantageously, the diversion mixture can improve the efficiency of the

An embodiment of the method of plugging a perforation cluster with the diversion mixture is described with reference to.illustrates a cemented well with multiple perforation clusters. Wellboreextends into formationand is a cemented well that is cased and lined. Perforation clusters,, andextend into the near-wellbore of formation. Whileis shown with three perforation clusters, one of skill in the art will appreciate that the number of perforation clusters can be determined to ensure coverage of the entire net pay of a reservoir.

When operating conditions indicate that the entire formation is not being stimulated simultaneously at least one of the perforation clusters is not receiving flow of the stimulation fluid and at least one of the clusters is receiving the flow of the stimulation fluid. When the wellbore contains more than two perforation clusters, any combination can be receiving flow simultaneously while others are in the absence of flow so long as at least one perforation cluster is receiving flow while at least one perforation cluster is in the absence of receiving flow.

In the embodiment shown in, perforation clusteris connected to the formation area with the lowest stress compared to perforation clustersandsuch that when stimulation fluidis introduced to wellbore, stimulation fluidcan flow to perforation cluster. Perforation clustersandare in the absence of flow of stimulation fluid.

Diversion mixture is introduced to redistribute the flow of the stimulation fluid to other perforation clusters. As shown in, after the diversion mixture is introduced, the diversion mixture also flows to perforation cluster. As the diversion mixture is pulled into perforation cluster, the rock salts and date palm seeds can block the perforation causing temporary plugto form. After temporary plugforms, the stimulation fluid can flow to other perforation clustersandcausing those parts of the near-wellbore formation and formation to be stimulated.

Advantageously and unexpectedly, the combination of date palm seeds and rock salts have a synergistic effect in isolating the perforation clusters. Rock salts alone are not effective to plug the perforation clusters because at the pressures and temperatures in the formation they will dissolve before the isolation can occur. In addition, large volumes of rock salts would be required.

Although the present invention has been described in detail, it should be understood that various changes, substitutions, and alterations can be made hereupon without departing from the principle and scope of the invention. Accordingly, the scope of the present invention should be determined by the following claims and their appropriate legal equivalents.

There various elements described can be used in combination with all other elements described here unless otherwise indicated.

The singular forms “a”, “an” and “the” include plural referents, unless the context clearly dictates otherwise.

Optional or optionally means that the subsequently described event or circumstances may or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur.

Ranges may be expressed here as from about one particular value to about another particular value and are inclusive unless otherwise indicated. When such a range is expressed, it is to be understood that another embodiment is from the one particular value to the other particular value, along with all combinations within said range.

Throughout this application, where patents or publications are referenced, the disclosures of these references in their entireties are intended to be incorporated by reference into this application, in order to more fully describe the state of the art to which the invention pertains, except when these references contradict the statements made here.

As used here and in the appended claims, the words “comprise,” “has,” and “include” and all grammatical variations thereof are each intended to have an open, non-limiting meaning that does not exclude additional elements or steps.